Modal verbs are a kind of auxiliary or helping verb. Auxiliary verbs cannot be used on their own and appear with a main verb.
The most common modal verbs are:
must ought to
Modal verbs affect the main verb they are associated with by expressing the level of possibility, ability, permission and obligation for that action or state.
They act differently to other verbs; they never change their form, regardless of whether in the singular or plural persons, or whether expressing the past, present or future.
affirmative: subject + modal + main verb in base form
I should run to the shop.
negative: subject + modal + not + main verb in base form
I should not run to the shop.
I shouldn’t* run to the shop.
interrogative: modal + subject + verb in base form
Should I run to the shop?
negative interrogative: modal + subject + not + verb in base form
Should I not run to the shop?
Shouldn’t* I run to the shop?
Modal verbs primarily express degrees of:
They can also be used to express:
In the negative they express the opposites, such as:
primarily used to express possibility, ability and permission
I can be with you at 9 a.m. (possibility)
She can swim underwater. (ability)
Yes, you can have an ice-cream. (permission)
Can you change this for a different colour please? (request)
Can I give you a hand? (offer/suggestion)
You can’t learn a new language if you don’t practice. (conditional)
used as the past tense of can, and also in conditional constructions
Mary could have been better than her sister at ballet. (possibility)
He could run the mile in 4 minutes when he was younger. (ability)
Could you pass me the salt please? (polite request)
I could go for you? (offer/suggestion)
If I could be President for one day, I would change the world. (conditional)
indicates that something will possibly happen, and to request and receive permission or emphatic refusal in the negative
She may come later. (possibility)
May I speak to Mr Jones please? (request)
You may go now. (permission)
You may not go to the party. (emphatic refusal)
indicates possibility and also used for polite request.
The train might be delayed. (possibility)
She might like a jewellery box for her birthday. (suggestion)
Might I have a glass of water please? (polite request)
used to make offers or suggestions, show intent and for formal directives, and in the negative expresses refusal
Shall we tell him? (offer/suggestion)
I shall go to the shops later. (intent)
Pupils shall not use the main entrance. (formal directive)
We shall not be moved! (refusal)
In traditional British grammar shall is used instead of will in the first person singular and plural (I, we) in Future tenses, but this has become less common now.
often used to express an opinion of what is considered to be correct by the speaker, to express an obligation or duty, or to make a suggestion
I should help my elderly mother more. (obligation)
You should write them a thank you letter. (opinion/obligation)
You should get up or you’ll miss the bus. (suggestion)
Should I order you a taxi? (offer)
The plane should be taking off any minute now. (prediction)
mainly used to express obligation and prediction, and is used for future tenses
You will need to show your boarding pass at the gate. (obligation)
Short hair will suit you. (prediction)
Will you take the dog for a walk please? (request)
She will come tomorrow. (intention)
past tense of will, and can express possibility, for polite requests and conditionals
I would never eat meat. (negative possibility)
Would you mind moving your chair please? (polite request)
If I was rich I would never work again. (conditional)
indicates definite possibility or certainty and strong obligation, and in the negative, must not or mustn’t, it expresses prohibition
She must be very bright to have got into the best university. (certainty)
You must get a visa before you can travel to China. (obligation)
You must visit the Van Gogh museum while you’re in Amsterdam. (recommendation)
expresses obligation and duty or an opinion of what is considered to be correct by the speaker
You ought to finish your homework before you go out. (obligation)
The painting ought to go up in value now that the artist has died. (opinion/possibility)
Our team ought to win the match today. (probability)
Contracted forms of modals
Modal verbs do not have contracted forms in the positive, but they do have contracted forms for the negative, with the exception of may
* will and would have other contracted forms :
Modals with another auxiliary
Another auxiliary verb may follow the modal verb:
They are often used with the verb to have
He might have to sell his car.
Modals without a main verb
Modal verbs may be used without a main verb if the meaning is understood:
May I have a biscuit?
Yes, you may.
Modals with adverbs
Adverbs usually come between the modal verb and the main verb:
She can rarely eat all her lunch.
Common mistakes to avoid with modals
Modal verbs only have one form which never changes (for example they do not take an -s in the third person singular)
He can swim well. (NOT swims)
Use the base form of the verb after the modal
He will go to senior school when he is 11.
Use not after the modal for negatives, or the individual shortened forms of the modals
You should not talk loudly in the library.
You shouldn’t talk loudly in the library.
Modal verbs are auxiliary verbs and they do not take another auxiliary to form the negative or questions.
Can vs May for permission
Traditionally can was used to mean physical and mental ability – to be capable of – rather than for permission. However, in informal speech can has become synonymous with asking or giving permission, and it is now more common to hear can used rather than may for permission, although may remains the more formal and polite form.
Can I have a biscuit? – is it possible for me to have a biscuit i.e. am I physically able to
May I have a biscuit? – am I allowed to have a biscuit
Although can is now commonly used for permission, many a child continues to be teased by a parent with the reply to the first question being, ‘You can, but you may not.’