Modal verbs

Present tense	Past tense
can	could
may	might
shall	should
will	would
must

General formal properties of modal verbs

• Modal verbs have only one form and do not inflect for person or number.
• Modal verbs do not have infinitive forms, either with to or without.
• Modal verbs have no -ing form and no -ed participle form and therefore lack progressive and perfect forms
• Modal verbs are placed first in the verb phrase and are followed by a verb in the base form. The next verb may be a lexical verb or an auxiliary verb (be, do, have) or the substitute verb do, but cannot be another modal verb.
• Modal verbs cannot be used as lexical verbs. (I must to bed, I should your help,)
• Modal verbs can only stand alone when the lexical verb is understood. (A: He might have a phone. B: Yes, he might.)

Form

Aspect \ Voice	Active	Passive
Simple	modal verb	modal be V3
Progressive	modal be verb-ing	modal be being V3
Perfect	modal have V3	modal have been V3
Perfect Progressive	modal have been verb-ing	modal have been being V3

Interrogatives: modal subject verb. Negative form: subject modal not verb

Usage

can

• ability
  • You can hear the atmosphere in the stadium.
• permission
  • You can borrow the car but be careful.
  • A: Can I smoke in here? B: No, I’m sorry you can’t.
• general-truths
  • Steel can resist very high temperatures
• possibility
  • How can they be there already? They only left ten minutes ago.

could

• Past tense of can ability
  • When I was a kid I couldn’t swim at all.
• probability
  • I think that could be the answer to the problem
• suggestions
  • I could just cook dinner tonight.
• permission
  • Could I talk to you for a moment?
• criticism
  • You could have told me. Why did you keep it all to yourself?
  • How could you forget that we’re going out to dinner tonight?
• past subjunctive
  • I wish I could fly!

may

• possibility
  • *That may be true
  • You may be right
• permission
  • May I go to the bathroom? Yes, you may
  • May I see that? No, you may not
  • You may leave the room
• wish hope subjunctive
  • May you both have a long and happy married life together.
  • May she rest in peace
  • May god bless you
  • May the weather be sunny
  • Wishes are often cast in the imperative (Have a great day!) rather than the subjunctive mood (May you have a great day) Subjunctive may lend a more formal, literary, or solemn feeling (perhaps jocularly so) to the wish.
  • Wishes in the subjunctive need not use may if the meaning is clear without it, which is the case mainly for established expressions in the third-person singular, such as God help you.

might

• possibility probability (less certain than may)
  • They might be at home.
  • I might see you tomorrow.
  • It looks nice, but it might be very expensive.
  • It’s quite bright. It might not rain today.
• permission (very formal)
  • Might I speak to Mrs Lutterworth?
  • Might I take the last biscuit?
• permission (in past tense)
  • He asked me if he might go to the party, but I haven’t decided yet.
  • They wanted to know if they might come later.
• possibility (in past tense)
  • I thought that I might go the next day.
• although
  • I might be in a wheelchair, but I still want to be treated as a lady.
• suggestions
  • You might like to try one of our wonderful desserts.

will

• future
  • He will play tennis tomorrow.
  • How long will you be staying in Paris?
• predictions
  • I think we’ll do it, but it won’t be easy
  • If she gets the right grades, she’ll go to university.
• ability
  • Unfortunately, only one of these gloves will actually fit over my hand.
  • This jar will hold a pint.
• requests
  • Will you pass me that newspaper please?
  • Will you send this letter to me, please?
  • Will you give that to Tony when you see him, please?
  • Will you pass me the salt, please?
• invitations
  • Will you join us for a drink after the concert?
• directives
  • (parent to child) Will you sit down and just be quiet!
  • (adult to a child who is refusing to pick up an object she has thrown on the floor) You will pick it up and you’ll pick it up now!
  • You will ring me as soon as you get there, won’t you?
  • You’ll do it this minute!
• habit
  • She’ll listen to music, alone in her room, for hours.
• disapproval
  • He will leave that door open every time he goes through!
  • Oh, I will keep banging my elbow on that shelf.

would

• see Conditionals
• future-in-the-past reported clauses
  • I knew that would cause a problem.
  • I knew I would graduate two years later
  • I never thought I would be so alone.
  • John left for the front; he would not return until five years later.
  • On my first day at University, I met the woman who would become my wife.
• past-habit
  • We would always go to the seaside for our holidays.
  • When we were younger, we would cycle out to the beach most summer Sundays.
• volition desire intention
  • I did ask him, but he wouldn’t give me an answer.
  • He said he would always love her.
• Responding
  • It was a freezing cold morning and the car wouldn’t start.
• hedging
  • I would always recommend a slightly softer bed than a harder one.
  • I’d say you are about 40.
  • I would imagine the job will take about two days.
  • I’d say he was about fifty.
• Polite requests
  • Would you please be quiet?
  • Would you mind leaving us alone for a few minutes?
  • Would you open the door for me, please?
• polite offers or invitations
  • Would you like a sandwich?
  • Would you have dinner with me on Friday?

shall

• future intentions
  • Shall is used instead of will with first person subjects in rather formal contexts to make predictions and to announce intentions or decisions. It is much less frequent than will
  • Shall not/shan’t is very rarer, but does occur in formal contexts to make predictions and announce intentions or decisions
  • I shall sing in the choir tomorrow.
  • I hope that we shall win the game.
• suggestions requests
  • Shall we go and have a walk in the garden?
  • Shall I help you with that?
  • Shall we go out later?
  • Let us examine that, shall we?
• directives
  • (notice in an aircraft cabin) This curtain shall be left open during takeoff and landing.
• obligation
  • Citizens shall provide proof of identity.

should

• desirable ideal duty propriety expediency obligation

  • He should have been here at five and he’s not here yet.
  • She should be wearing glasses.

• possibility probability future

  • They should have it finished by Friday.
  • When you press this button, the pilot flame should ignite.
  • You should be warm enough with that coat.

In AmE, the present subjunctive is commonly used instead of should (e.g., “suggest that he stay”), while in BrE, should is commoner (e.g., “suggest that he should stay”).

must

• duty obligation imperative
  • You must arrive in class on time.
  • This door handle must be rotated fully.
• prohibition
  • He must not fight with his sister.
• probability
  • The children must be asleep by now.

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Comparisons

can, could and may

permission

Could is usually heard as more formal and polite than can, and may is the most formal/polite of the three.

probability

Can refers to what the speaker believes to be a factor to be usually the case. Could and may refer to possible events. Could and may rather than can are used to speculate about whether something is true or possible.

could, may and might

probability

Could, may and might are all used to express degrees of certainty. May expresses a slightly greater degree of certainty than could, and tends to be used in more formal contexts. Might is more tentative than may or could.

Replacements for Modal

• The modals can and could, in their meanings expressing ability, can be replaced by am/is/are able to and was/were able to. Additional forms can thus be supplied: the infinitive (to) be able to, the subjunctive and (rarely) imperative be able to, and the participles being able to and been able to.
• The modals may and might, in their meanings expressing permission, can be replaced by am/is/are allowed to and was/were allowed to.
• The modal must in most meanings can be replaced by have/has to. This supplies the past and past participle form had to, and other forms (to) have to, having to.
• Will can be replaced by am/is/are going to. This can supply the past and other forms: was/were going to, (to) be going to, being/been going to.