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What are Modal Verbs? The following article lists and explains the nine modal verbs in English and discusses some of the possible definitions and meanings of these modal verbs. The nine modals verbs in English are: * can * could * may * might * must * shall * should * will * would Position of Modal Verbs Modal verbs always appear in the first position at the beginning of the verb phrase in English. Unlike other verbs, modal verbs do not show tense or number. The eight possible verb phrase combinations that contain modal verbs in English are: * modal verb + base form = will eat * modal verb + be + present participle = will be eating * modal verb + have + past participle = will have eaten * modal verb + be + past participle = will be eaten * modal verb + have + been + present participle = will have been eating * modal verb + have + been + past participle = will have been eaten * modal + be + being + past participle = will be being eaten * modal verb + have + been + being + past participle = will have been being eaten Although most varieties of English only allow for the use of one modal verb per verb phrase, some English dialects such as Southern American English allow for multiple modals. For example, the double modal might could as in He might could build a new machine shed expresses both possibility and ability. However, prescriptive grammars proscribe against the use of double modals. Some Definitions of English Modal Verbs Modal verbs are difficult to define in any language because of the wide range of pragmatic uses of modal verbs by native speakers. Some of the more common definitions (in no particular order) of the modal verbs in English are: * can – ability, permission, possibility, request * could – ability, permission, possibility, request, suggestion * may – permission, probability, request * might – possibility, probability, suggestion * must – deduction, necessity, obligation, prohibition * shall – decision, future, offer, question, suggestion * should – advice, necessity, prediction, recommendation * will – decision, future, intention, offer, prediction, promise, suggestion * would – conditional, habit, invitation, permission, preference, request, question, suggestion 1. Modal verbs do not take "-s" in the third person. Examples: * He can speak Chinese. * She should be here by 9:00. 2. You use "not" to make modal verbs negative, even in Simple Present and Simple Past. Examples: * He should not be late. * They might not come to the party. 3. Many modal verbs cannot be used in the past tenses or the future tenses. Can They can control their own __________. We can’t fix it. Can I smoke here? Can you help me? Could Could I borrow your dictionary? Could you say it again more slowly? We could try to fix it ourselves. I think we could have another Gulf War. He gave up his old job so he could work for us. May May I have another cup of coffee? China may become a major economic power. Might We'd better phone tomorrow, they might be eating their dinner now. They might give us a 10% discount. Must We must say good-bye now. They mustn’t disrupt the work more than necessary. Ought to We ought to employ a professional writer. Saying what’s right or correct Shall Shall I help you with your luggage? Shall we say 2.30 then? Shall I do that or will you? Should We should sort out this problem at once. I think we should check everything again. Profits should increase next year. Saying what’s right or correct Will I can’t see any taxis so I’ll walk. I'll do that for you if you like. I’ll get back to you first thing on Monday. Would Would you mind if I brought a colleague with me? Would you pass the salt please? Would you mind waiting a moment? "Would three o`clock suit you?" - "That’d be fine." Would you like to play golf this Friday? "Would you prefer tea or coffee?" - "I’d like tea please." |
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Examples of Modal Verb Usage The following sentences are examples of usage of modal verbs in English. For example, the following four sentences all ask for permission but with different degrees and types of modality: * Can I go to the bathroom? (asking for permission) * May I go to the bathroom? (more politely asking for permission) * Could I go to the bathroom? (asking for permission with less certainty) * Might I go to the bathroom? (asking for permission with uncertainty) The following sentences also demonstrate the subtle meanings in regards to modal verbs of suggestion: * You could listen to me. (suggestion) * You might listen to me. (uncertain suggestion) * You should listen to me. (strong suggestion) * You must listen to me. (stronger suggestion) * You will listen to me. (strongest suggestion) The meanings of modal verbs are very pragmatic and must be learned through use. Modal Verbs Practice Exercise Identify the modal verb and modality (definition) in the following sentences. Sentences 1. You could ride your bike across the ______, but I advise against it. 2. Since all dogs are mammals, this golden retriever must be a mammal. 3. You might consider finishing your degree. 4. I will finish my essay tonight even if I have to forgo sleep. 5. The puppy can sit on command. 6. I would eat cereal every day as a child. 7. You may encounter some difficult patrons on occasion. 8. The train should arrive in a few minutes. 9. The situation would not be so bad if we all remained calm. 10. I will have earned my graduate degree next spring. Possible Answers 1. could – possibility 2. must – deduction 3. might – suggestion 4. will – intention 5. can – ability 6. would – habit 7. may – probability 8. should – prediction 9. would – conditional 10. will – future "English has nine full modals verbs as a well as four quasi-modal verbs, which possess some but not all properties of prototypical modals. The nine English modals are can, could, may, might, must, shall, should, will, and would. The four quasi-modals in English include ought to, used to, would rather, and had better (had best) (Palmer 1990: 5; Palmer 2003:12).[1] The verbs need and dare also resemble modal verbs within negated, but not positive, verb phrases as in He need not whine and She dare not complain (Huddleston 1984:165). |
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THEME 20. AUXILIARY VERBS AND MODALS: FORMS AND FUNCTIONS.
Introduction. Verbs may be defined as important parts of the speech, even if they are not overtly present in our messages their meaning remains latent. So, for instance Eckersley observes that the verb is the most important part of the speech in the great majority of the sentences. We can consider a verb according to the traditional definitions as: A word that expresses something about a person, an animal or thing. A part of the speech by which we are able to say what a person, animal or thing is or does, or what is done to that person, animal or thing. The part of the speech that assists in predication asks a question or expresses a command. # Verb classification. According to Quirk verbs can be classified in the two major types: Auxiliary verbs and lexical verbs. * Auxiliary verbs. Auxiliaries may be defined as their name indicates as helping verbs since they have no independent existence as verb phrases but only help to make up verb phrases. They must compulsorily be followed by a lexical verb and are structurally necessary for certain constructions, especially negatives and questions. # Primary auxiliaries. They have a purely grammatical function and are inflectionally marked in the 3rd person singular. This group is made up by three: BE, HAVE, DO. # DO. It is the most neutral of all the auxiliaries. It has no individual meaning but serves as an operator for the formation of the interrogative and the negative of the present simple and past simple tenses and also for emphasis or to convey a coherent style. There is also a lexical verb do (= perform) which has the full range of forms including the present participle doing and the past participle done. Do as an auxiliary verb is required in the following cases: * To form negative sentences when the verb is imperative, simple present or simple past. * In questions involving inversion where the verb is in the simple present or past tense. There is no do-periphrasis in positive wh-questions beginning with the subject ( What happened?) And in yes-no questions where inversion is not necessary. ( He said that?) * In emphatic expressions where the verb is simple present, simple past or imperative. Do sit down! He did say he would be here at six. You do look nice today! * In sentences with inversion caused by certain introductory words such as the negative adverbs never, hardly, etc, when the verb is in the simple present or past tense. Never did he think that the book would be finished. * To avoid repetition of a previous ordinary verb ( pro-form) * Comparisons: He sings better than you do. * Tag questions: You went to the doctor's, didn't you? * In short answers: Do you smoke? Yes, I do. Do as a lexical verb is used in: * How do you do?, is said by both parties after the introduction * Meaning be adequate in expressions such as: I haven't got a torch. Will a candle do? * Meaning it is not your business, it's not your concern in: It is nothing to do with you. * Meaning perform: in this case it constitutes a challenge for the Spanish student because it is difficult to distinguish between make and do. - talk about work: I must do the accounts.. - When we won't say exactly what the activity is. What shall we do now! Do something! We use do to - To talk about longer and repeated activities - Before determiner + -ing form. Can you do the shopping. # Have. As a primary auxiliary it is used for: * The formation of the perfective aspect by combining with past participles. * The formation of the causative ( have + object + P.P.): I had my car washed. It can also be used instead of a passive verb to convey the idea of accident or misfortune: He had two of his teeth knocked out in the match (Here the subject is the person who suffers the result of the action; in the previous example the subject was the person who orders something to be done. * It is used as an auxiliary for the expression of duties, obligation: have to. As a lexical verb it can be constructed either as an auxiliary ( without do periphrasis) or as a lexical verb ( with do-periphrasis). Depending on the meanings and the variety used (BrE or AmE) it will be constructed in one way or the other. It is used: * For the expression of possession: in this case it is constructed as an auxiliary verb in BrE but AmE prefers the do-construction. I haven't any books. (BrE) I don't have any books ( AmE) In BrE the normal spoken form (informal) uses got in the present. In AmE got forms are also possible in informal speech and have drops in very informal speech: (AmE) I(`ve) got a problem. (Have) you got a light? When it expresses an habitual action BrE also uses do periphrasis: Compare: I haven't got any whiskey. We don't usually have whiskey in the house. * It is also used as dynamic verb with the sense of receive, take, experience. Here it takes do-periphrasis in both AmE and BrE. Do you have a cup of tea for breakfast? # BE. As an auxiliary: * Aspect auxiliary: to form continuous or progressive tenses. * Passive auxiliary * Be + infinitive: * To convey orders or instructions No one is to leave the building now. * Was/were + inf: conveys the idea of destiny: They said goodbye, little knowing they were never to meet again. * Be about to: immediate future: I am about to leave. As a lexical verb it has got many uses that do not coincide in Spanish and in English We use it in English to * Denote existence or giving information: He is a teacher. * To talk about age, weather condition, distance, time. * Be in the imperative can mean: pretend: You be the fairy godmother and I'll be Cinderella. Become: Be a good cooker! As lexical verb it may have do-periphrasis in: * Persuasive imperative sentences. Do be quiet! * Negative imperatives: Don't be naughty. # Modal auxiliaries. # General features of modal auxiliaries. The group of properties that modals fulfil are the so called NICE properties: N: they make the negative with not, they do not need an operator. I: They do not take inversion to form interrogatives. C: They can express code on their own. Interrogatives do not need auxiliaries and they can form short answers on their own ( Yes, I can.) E: Emphasis Apart from these there are more features that modal auxiliaries share: * They do not have infinitive form, they do not take TO before them. * They are all followed by the infinitive which is bare except with ought o and used. They do not have inflection in the third person singular of the present form. * Two modals can never go together: * I can must. * They are limited in the range of time reference. * They are negatively affected by overlapping: one single modal verb may be used for a multiple and varied set of communicative functions. # Classification of modality. We have epistemic and deontic modality. EPISTEMIC: deduction, possibility, prediction. DEONTIC: obligation, advice, permission, prohibition. # Kinds of modal verbs. * CENTRAL: the typical, can, should… * SEMI-MODALS: sometimes they function as modals and sometimes they don't: need, dare. * MODAL IDIOMS: idioms that express modality: had better, would rather… * Central modals: CAN/COULD. * Ability: be able to, know how to, be capable of… He can play the guitar very well. * Theoretical Possibility: Can and could express general possibility as in You can sky on the hills (= it is possible because there is enough snow) or occasional possibility ( very much used related to people's behaviour) as in Measles can be dangerous (=Sometimes it is possible for them to be dangerous) My mother can be very shy. * Permission: It is used in much more informal situations than may. Another difference with may as related to permission is given in the following statements: You may park here ( I give you permission) You can park here ( Could be mine or others permission) * MAY/MIGHT. * Factual Possibility: May/ might + present infinitive: It indicates a chance that something is possible: You may/might be right (=it is possibly true at the moment of speaking) He may/might tell his wife (=a chance that something will happen in the future). Normally either can be used but, might increases the doubt ( might is not the past of may; it means possible but less likely) May is not used in the interrogative unless it occurs after a wh- particle, but it is better to use a paraphrase with to be likely to, do you think. Compare. * May he be at home? When may we expect you? (= When are you likely to arrive? May/might + perfect infinitive: It is used when you are not certain about a past action. When the uncertainty no longer exists in the present (i.e. something did not happen but it was possible) then only might + perfect infinitive is possible. You shouldn't have drunk that wine. It may have been drugged (=we are still uncertain if it has been drugged or not) You shouldn't have drunk that wine. It might have been drugged (=he or we know yet it wasn't drugged) * Permission: It is used for more formal and less common contexts than can. May emphasises and authoritarian overtone. ( See can) * There is a rare use of may as a quasi-subjunctive auxiliary to express wish, normally in positive sentences. May the best man win! May you have a long and happy life! * SHALL. Shall is, on the whole and especially outside BrE, an infrequent auxiliary with restricted use compared with would, should, will. It is only in the first person of questions that it cannot be replaced by will. Shall I come now? * Will I come now?. Apart from this meaning of intention on the part of the speaker it has also other meanings although not very much used today. o Willingness on the part of the speaker in 2nd and 3rd person ( weak volition) He shall get his money. You shall do exactly as you wish. o Insistence ( strong volition) and legal: You shall do as I say. He shall be punished. Shall can also be used today to: o Express suggestions: Shall we go scuba diving? o In emphatic expressions: We shall go and we shall win. o OUGHT TO AND SHOULD Both are used to express obligation and logical necessity but they are less categorical than must and have to . Although they have similar meanings should is used in a more subjective way, you give the subjective opinion about something and ought to is for a more objective use. Compare: You should/ought to go and see Mary some time (=subjective opinion about something) We ought to go and see Mary tomorrow, but I don't think we will. ( “should” could not be possible here because you cannot give an advise to yourself knowing beforehand that you are not going to fulfil it) Followed by the continuous infinitive ( ought to/should + continuous infinitive) it refers to someone that is not fulfilling his obligation. He ought to be studying for his exam. He shouldn't be spending his time on the beach. Apart from the uses mentioned above Should is also used : + As a putative after certain expressions: I am sorry that this should have happened. + Tentative condition in conditional clauses: If you should change your mind, please let us know. + WILL/WOULD. Both verbs express weak volition (He will help you if you ask him/ Would you excuse me?) and insistence (strong volition): He will do it whatever you say/ It's your own fault: you would take the baby with you. But they have independently other meanings: WILL: # Intention: In this case it is usually contracted. I'll write as soon as I can. # Prediction: The game will be finished. WOULD # Characteristic activity: Every morning he would go for a long walk. # Hypothetical meaning in main clauses: He would smoke too much if I didn't stop him. # Probability: That would be his mother. + MUST. + Obligation in the present tense (= be obliged to, have to). The past tense is supplied by had to . In this sense mustn't is not the negative, this form means not allowed to. To convey the idea of no obligation we should use don't have to, not be obliged to, needn't. The difference between must and have to is seen in the following example: Mother: You must wipe your feet when you come in.( the speaker is the authority) Small boy: I have to wipe my feet every time I come in ( the speaker is not the authority) Must, used in the 1st person singular denotes the idea of urgency: I must phone my mother and tell her the news (=you feel that the obligation is something urgent) + Deduction: To say that something is logically necessary or that we suppose that it is certain. There is an ambulance at Peter's door: he must be ill ( that is the only possibility since he lives alone) Must is not used in the negative, the negative is done with can't; and it is only used in the interrogative when carrying a deduction: It must be Tom. Why must it be Tom? Other people use that flat. In other cases Can is preferred for the interrogative. + Root necessity: this conveys the idea of something that is essential or necessary. Plants must receive a good supply of sun and moisture. + USED TO It always takes the to infinitive and occurs only in the past tense. It may take do-periphrasis, in which case the spellings didn't used to and didn't use to both occur. The interrogative construction used he to? is especially BrE; did he used to? is preferred in both AmE and BrE. It is used to express a state or habit that existed in the past but has ceased: He used to play cards a lot ( but he doesn't do it now). The difference between this verb and Would is that: # used to is used when there is a contrast between past and present: I used to smoke cigarettes, but now I use a pipe. # Would is used to express a past routine and pattern but there is no contrast with the present, it is just a description of someone's routine during a certain period: Every morning he would go for a walk (= there is no the idea that he does no longer do it) + : Semi-Auxiliaries: NEED & DARE. Need and dare are considered semi-auxiliaries because they can be constructed either as modal auxiliaries ( with the bare infinitive and without any inflected -s form) or as lexical verbs ( with the to - infinitive and with the inflected form -s forms). The modal verb construction is restricted to non-assertive contexts (i.e. mainly negative and interrogative sentences) whereas the lexical verb construction can always be used and is in fact the more common. NEED As an auxiliary verb in negative terms it indicates absence of obligation. It expresses the speaker's authority or advise and it is used for the present and the future: You needn't type your essay ( the speaker is the authority, it could be the teacher for example) But it can also take do-periphrasis and in this case it expresses absence of obligation as well but in this case the speaker is not the authority: you don't need to type your essay ( here it could be a conversation among classmates) As a lexical verb it means “require” : I need some money/ your hair needs cutting. DARE It is not a common verb in informal style. But in few cases it is still common in spoken style: # In BrE the negative daren't is frequent: I daren't ask her. # Children to challenge each other to do frightening things: I dare you to ride your bike through the gate with no hands. # To discourage people from doing things they shouldn't: mummy can I draw a picture on the wall? - you dare !Don't you dare. # I dare say it will rain soon ( it will probably…) # How dare you? Take your hands off me immediately. ( Indignation) With this meaning do takes the do perphrasis. Since can has no passive form it is expressed by allowed to: I was allowed to park here. But may/might may form part of a question: Do you think he might not be able to wait? Quirk It also helps to convey the idea of wonder: How old may he be? Accompanied by well it is used idiomatically meaning there is a good reason for: you may say well so. And in adverbial clauses of concession it emphasises the aforementioned idea. Quirk If more people lived with him we couldn't use must but may.
Modals - English Grammar1) can
2) could
3) may
4) might
5) must
6) must not/may not
7) need not
8) ought to
9) shallinstead of will in the 1st person
10) should
11) will
12) would
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WouldWould is an auxiliary verb, a modal auxiliary verb. We use would mainly to:
We also use would for other functions, such as:
Structure of Wouldsubject + would + main verb The main verb is always the bare infinitive (infinitive without "to").
Notice that:
Use of Wouldwould: Talking about the pastWe often use would as a kind of past tense of will or going to:
Using would as as a kind of past tense of will or going to is common in reported speech:
We often use would not to talk about past refusals:
We sometimes use would (rather like used to) when talking about habitual past behaviour:
would: Future in pastWhen talking about the past we can use would to express something that has not happened at the time we are talking about:
would: ConditionalsWe often use would to express the so-called second and third conditionals:
Using the same conditional structure, we often use would when giving advice:
Sometimes the condition is "understood" and there does not have to be an "if" clause:
EC TIP: Although there is always a main verb, sometimes it is understood (not stated) as in:
would: Desire or inclination
would: Polite requests and questions
would: Opinion or hope
would: Wish
EC TIP: Note that all of these uses of would express some kind of distance or remoteness:
would: Presumption or expectation
would: Uncertainty
would: Derogatory
would that: Regret (poetic/rare) - with clauseThis rare, poetic or literary use of would does not have the normal structure:
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Would, should and could are three auxiliary verbs that can be defined as past tenses of will, shall, and can; however, you may learn more from seeing sentences using these auxiliaries than from definitions. Examples of usage follow. Would Technically, would is the past tense of will, but it is an auxiliary verb that has many uses, some of which even express the present tense. It can be used in the following ways: * To ask questions: Would you like some coleslaw? = Do you want some coleslaw? Would you turn in your assignment now? = Please turn in your assignment now. * With who, what, when, where, why, how: How would the neighbors react? What would you do if I sang out of tune? In the two sentences above, would means about the same thing as will. * To make polite requests: I would like more coleslaw, please. = I want more coleslaw, please. I would like you to sit down now. = I want you to sit down now. * To show a different response if the past had been different: I would have helped you if I had known you were stranded. (I didn't know that you were stranded. This "not knowing" occurred before my not helping you.) John would've missed the trail if Mary hadn't waited for him at the stream. (First Mary waited for him. If her response had been to not wait, then next John would have been on the wrong trail.) * To tone down strong, controversial statements-not recommended in formal essays: I would have to say that you're acting a bit immature. Here would has a similar meaning to do but less emphatic. * To explain an outcome to a hypothetical situation: Should I win a million dollars, I would fix up my house. Think of should as if, and would as will. * To show habitual past action: Helen would sob whenever John would leave home. Think of would as did. * To show repetitive past action: For a moment the plane would be airborne, then it would bump back down along the hard earth. (The plane was in the air and then back on the ground several times.) * To show preference between two choices, used with rather or sooner: I would sooner die than face them. = I prefer death in place of facing them. I would rather handwrite than type. = I prefer handwriting instead in typing. However, the second choice may by implied but not stated: I would rather die. Implied is that I would rather die than...do whatever it is that the context has provided as an alternative to dying. * To show wish or desire: Those people would allow gambling. = Those people want to allow gambling. Would it were so. = I wish it were so. (Infrequently used) We wish that he would go. = We want him to go. * To show intention or plan: She said she would come. = She said she was planning to come. * To show choice: I would put off the test if I could. This means my choice is to delay taking the test, but I do not have the ability to delay taking it. * To express doubt: The answer would seem to be correct. = The answer is probably correct. * To show future likelihoods relative to past action: He calculated that he would get to the camp around 6 p.m. The men would have dinner ready for him. The first sentence means he believed his camp arrival time was going to be about 6:00 p.m. The "calculating" (or believing) happened in the past, yet the arrival is going to occur later. The second sentence predicts that, at that future time, dinner will be ready for him. * Strange but true: Notice how changing have to had can change the way would works: Would you had changed your mind. = I wish you had changed your mind. Would you have changed your mind. = If circumstances had been different, is it possible that you might have changed your mind? Should Technically, should is the past tense of shall, but it is an auxiliary verb with a few uses, not all of which are in the past tense, namely, the following: * To ask questions: Should you have erased the disk? = Were you supposed to have erased it? Should I turn in my assignment now? = Am I supposed to turn in my assignment now? Here, should means about the same thing as ought. * To show obligation: You should floss and brush your teeth after every meal. Think of should as supposed to, as in the previous example, but here to make a persuasive statement. * To show a possible future event: If I should find your coat, I will be sure to call you. Think of should as do; furthermore, should could be left out of the above sentence, leaving, "If I find your coat, I will be sure to call you." Alternately, if could be left out of the sentence: "Should I find your coat, I will be sure to call you." * To express a hypothetical situation: Should you wish to do so, you may have hot tea and biscuits. = If you wish to do so, you may have hot tea and biscuits. * To express what is likely: With an early start, they should be here by noon. Think of should as ought to or probably will. * To politely express a request or direct statement: I should like to go home now. = I want to go home now. I should think that a healthy forest program is essential to any presidential victory.= I think that a healthy forest program is essential to any presidential victory. Could Technically, could is the past tense of can, but it is an auxiliary verb with a few uses, not all of which are in the past tense, namely the following: * As the past tense of can: In those days, all the people could build houses. = In those days, all the people had the ability to build houses. * To ask questions: Could you have erased the disk? = Is it possible that you erased the disk? Could I leave now? = May I leave now; am I allowed to leave now? * To show possibility: You could study harder than you do. = You have the potential to study harder than you do. He knew the sunset could be spectacular. = He knew that the sunset was sometimes spectacular. * To express tentativeness or politeness: I could be wrong. = I may be wrong. Could you come over here, please? = Please come here. In conclusion, you could use these three auxiliaries if you would, and you should! Write a sample sentence for each possible usage of could, would, and should; then ask any Reading/Writing or English tutor for further assistance. |
Modal verbs, also called modal auxiliaries or simply modals, are a type of auxiliary verb or helping verb. English has ten modal verbs:
can could may might shall should will would must ought to
Modals express the mood a verb, such as ability, possibility, necessity, or another condition. They are used with a main verb to form a sentence or a question. Modals are not conjugated, have no tense, and cannot be used without a main verb.
When used with modal verbs (except ought), main verbs always remain in the infinitive without to.
In a statement the word order is subject + modal + main verb.
subject modal main verb They can come. Mike should walk.
In questions, the word order changes to modal + subject + main verb.
yes-no questions modal subject main verb Can they come? Should Mike drive?
wh- questions wh- word modal subject main verb When can they come? How could he know?
Can
The modal can indicates possibility or ability:
Tom can help you.Wild animals can be dangerous.
Dining out can be costly.
In questions, the modal can requests permission to do something or to ask about possibilities:
Can I help you?Can Mike come over for dinner?
Who can answer the next question?When can we get back the results?
Could
Could indicates possibility or ability in the past:
I could have told you that.It could have been a disaster.
When I was young, I could run very fast.
Could speculates about future posibilities. In the following examples could and might are synonomous.
It could / might rain tonight.
That could / might be dangerous.
In yes-no questions, could speculates about present posibilities:
Could she be the murderer?Could this be a mistake?
It can also make a request. In these examples could and can are synonomous, but could is more polite.
Could / Can you open your window?Could / Can you help me move this sofa?
Could indicates an option:
We could go see a movie.I could become a doctor.
The modal could is also used to form the conditional. The conditional contains an if clause and a result clause. Could is placed in the result clause.
In these examples, could expresses hypothetical situations:
If I had time, I could play tennis with you.We could study together, if you want to.
If it weren't raining, we could go on a picnic.
Could mentions something that didn't happen because a certain condition was not met:
If we had left sooner, we could have taken the train.I could have passed the exam if I had studied more.
I'm glad we took umbrellas. We could have gotten soaked.
Shall and Will
The modals shall/will + main verb are used to create future tenses. These modals indicate an intention or an action that is expected to happen in the future.
When used in statements, there is no difference in meaning between these two modals; however, shall is rarely used in American English.
I will / shall close the door for you.Tom will / shall meet us at the train station.
They will / shall leave tomorrow at 8:00.
In wh- questions, shall and will ask about options.
Who will / shall drive the car?When will / shall I see you again?
How will / shall you get here?What time will / shall we meet?
In yes-no questions, shall and will have different meanings.
Will asks a favor.
Will /
Shallyou turn off the TV?Will /
Shallyou stop whining?Will /
Shallyou go with me?
Will also asks for information or knowledge about somebody or something.
Will /
ShallTom ever pay you back?Will /
ShallMars be visited by humans within twenty years?Will /
Shallyou be finished soon?
Shall asks about a preference. In these examples, shall and should are synonomous. In American English, shall is rarely used; when it is, it's only in the first person singular and plural.
Should / Shall I close the door?Should /
Shallhe close the door?Should /
Shallthey come back later?Should /
ShallTom bring food to the party?Should / Shall we stay here?
May and Might
The modals may and might indicate an uncertain future action. These two modals are synonymous.
I may / might go to the park, or I may / might stay home.This may / might be a bad idea.
It may / might rain tonight.
iMay or can gives instructions or permission.
You may / can now board the airplane.You may / can begin the exam in ten minutes.
In yes-no questions that make a request, you can use may or can. May is more polite.
May / Can I see your driver's license?
May / Can we have some more water, please?
You can might in place of may or can, but this is extremely rare in American English.
May / Can / Might I be of some assistance?May / Can / Might we offer you a suggestion?
Must
The modal must indicates an obligation.
You must see this movie.Tom must see a doctor immediately.
Must also indicates an assumption or probability.
My watch must be broken.He must have done that before moving to Spain.
In wh- questions, must is an obligation and can be replaced with the modal should. In American English, should is much more common in these types of questions.
When should / must we be there?Who should / must I talk to?
Must can sometimes form rhetorical questions, when you want the person to stop doing something.
Must you make so much noise? = Please be quiet. Must he ask so many questions? = I hope he stops asking questions.
Should and Ought (to)
The modals should and ought to indicate an obligation. These two modals are synonymous.
You should / ought to call your mother.I should / ought to go home now.
When used in questions, should asks if an obligation exists. Ought is never used in questions in American English.
Should he call her?Should we pay now?
When should we leave?What should I wear?
Would
Would followed by like is a polite way of stating a preference.
I would like white wine with my fish.We would like a room with a view.
In questions, would + subject + like is a polite request for a choice to be made.
Would you like soup or salad with your meal?Where would you like to eat dinner?
When would Tom like this delivered?
Would can make a request sound more polite.
Come here! Would you come here? Stop making that noise! Would you stop making that noise?
Would explains an action as a result of a supposed or real condition.
I would go with you if I didn't have to work.If I had not had to work, I would have gone with you.
She would be surprised if you came to the party.
Tom would drive, but he doesn't have a license.
Would introduces habitual actions in the past.
When I was a student, I would go swimming every day.When Tom lived in France, he would write me long letters.
http://html.rincondelvago.com/auxiliary-verbs-and-modals.html
http://www.englisch-hilfen.de/en/grammar/hilfsverben2.htm