Core modal verbs have only one form. They have no to-infinitive form, -ing form, past form or -ed form. We have to reword what we want to say by using other expressions:
I’d love to be able to see the Taj Mahal one day.
I’d love to can see the Taj Mahal one day.
They had to sell their house.
They musted sell their house.
Affirmative (+) forms
Modal verbs are placed first in the verb phrase (after the subject) and are followed by a verb in the base form. The next verb may be a main verb or an auxiliary verb (be, have):
Modal verbs do not change form for tense or person. Modal verbs can be followed by the substitute verb do:
We thought he might sell the houseB:
Yes, he could do.
Modal verbs cannot be used with another modal verb:
Windsurfing can be difficult.
Windsurfing can might be difficult. or Windsurfing might can be difficult.
Modal verbs always go before other verbs in a verb phrase:
[in a restaurant after a meal]
I think the bill could be expensive.
I think the bill could expensive.
You can go swimming, go for a long walk or visit the exhibition.
You can swimming, go for a long walk or visit the exhibition.
Modal verbs can only be used alone when the main verb is clearly understood:
She could take the bus.B:
Yeah, that’s true. She could. (She could take the bus.)
He may be wrong, you know.B:
Yes, he may. (Yes, he may be wrong.)
Negative (−) forms
Negatives are formed by adding ‘not’ after the modal verbs. We don’t use don’t/doesn’t/didn’t with modal verbs:
We can’t hear very well at the back.
We don’t can hear very well…
Question (?) forms
The subject and the modal verb change position to form questions. We don’t use do/does/did:
Could you help me?
Do you could help me?
Will it be a problem?
Does it will be a problem?
Why can’t you come too?
Why don’t you can come too?
We use modal verbs in question tags:
You can’t live like that, can you?
It could be any of those things, couldn’t it?
In speaking shall and will are often contracted to ’ll and would is contracted to ’d, especially when they follow a pronoun:
I’ll see you later.
We’ll never get there.
I knew they’d love it.
The negative forms of modal verbs are often contracted.
cannot (usually written as one word not two)
*won’t /wəʊnt/ or ’ll not
*shan’t /ʃɑnt/ or ’ll not
*wouldn’t /ˈwʊdənt/ or ’d not
* is the more common of the two forms.
Modal verbs and adverbs
We usually put adverbs in mid position between the modal verb and the main verb:
Loud noises may sometimes frighten dogs and other animals.
You’ll probably notice something different about the house.
When the main verb is understood, we can put the adverb between the subject and the modal verb:
I can never remember Flo’s number.B:
I never can either. (I can never remember Flo’s number either.)
Dare, need, ought to and used to (semi-modal verbs)
Dare, need, ought to and used to are often called semi-modal because in some ways they are formed like modal verbs and in some ways they are like other main verbs.
Like modal verbs, ought to and used to do not change form for person. Needn’t and daren’t do not have a third person -s in the present:
It used to be so easy. It ought to be easy now.
She needn’t worry.
John daren’t tell Ruth about the accident.
Like main verbs, the negative form of need, dare and used to is made by using do. But it can also be made without using do (like modal verbs).
The negative form of ought to is not made with do:
We oughtn’t to spend so much money.
We don’t ought to spend so much money.
Like main verbs, the question form for need, dare and used to is made by using do:
Does she need to get a camera before she goes away?
Did you use to play football when you were a child?
Question and negative forms of ought to are rare.