English Modal Verb Guide | to describe ability, obligation, possibility

Modal Verbs to Describe Possibility, Obligation & Ability

What are modal verbs?

These verbs: will, would, shall, should, can, could, may, might, are English modal verbs and follow special rules in English grammar.

1. Negative form: followed by not or n’t
musn’t, should not, couldn’t, shall not, will not

2. Question form: before subject
Could you help me, please ?
Would you like a beer?

3. They have only one form: they have no infinitive, present particlple or past participle, or –s termination.

4. These verbs are followed by an infinitive without to
We should call Bob about the party. (not We should to call Bob about the party)

What are semi modals?

Semi modals are verbs which have some of the charcteristics of modal verbs. For example:
need, have to / have (got) to, ought to and used to

Which modal verbs do I use for describing ability / inablity?

cancan’t [present]

Bob can drive a car.
I can’t speak italian.

couldcouldn’t [past forms]

If I could concentrate better, I wouldn’t waste so much time.
When I was young, I could play soccer really well.
I couldn’t visit my grandmother last week because I was ill.

Note: be able – unable can be used in the same way.

I was unable to finish the last few questions of the test.
We were able to book a hotel at the last minute.

Which modal verbs do I use to talk about possibility?

may (not), might (not), can, could

When do I use may and might?
may and might are normally used to describe something specific.
may is more certain than might or could.

You may have problems connecting to the Wi-Fi in this area. (speaker is more sure that the connection is problematic)
You might / could have problems connecting to the Wi-Fi in this area. (speaker is less sure that the connection is problematic)

When do I use can?
can is normally used for more general, theoretical possibility.

Computers can have problems. (= computers sometimes crash)

Which modal verbs do I use to talk about obligation?

Strong obligation
must, mustn’t, have to, (informal) have got to

We use must for strong present and future obligations, when we talk about rules, laws, regulations and conditions inposed by the speaker

I must leave now, I have to meet someone very soon. (imposed by the speaker)
You mustn’t drink and drive. (law, regulation, rule)
You must pay your taxes when they are due. (law, regulation, rule)

have to / have got to
We use have to / have got to when we talk about strong obligations in the present and future which are NOT imposed by the speaker.

We have to finish this project for university this week.(=obligation from the professor)
My father has got to go back to the hospital on Tursday. (=the doctor’s instructions)

    TIP: if you are not sure whether to use must or have to – use have to

had to

We use had to when we talk about obligations in the past

When I was a child I had to walk to school every day.
My teacher said I had to take more care with my English spelling.
We had to move when my father got a new job last year.

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