Uses of Modal Auxiliary Verbs

The modal verbs include can, must, may, might, will, would, should. They are used with other verbs to express ability, obligation, possibility, and so on.

Modal verbs are unlike other verbs. They do not change their form (spelling) and they have no infinitive or participle (past/present). The modals must and can need substitute verbs to express obligation or ability in the different tenses.

Modals are auxiliary verbs. They do not need an additional auxiliary in negatives or questions. For example: Must I come? (Do I must come?), or: He shouldn't smoke (He doesn't should smoke).

Uses of Modal Auxiliary Verb

      1. Can:

Ability	I can walk ten miles at a time.
permission	You can go.
Seek permission	Can I talk to you?
Possibility	I can go to your house.
Request	Can you help me with some money?

      2. May

Possibility (less than can)	He may come to my house.
Seek permission gently	May I come in?
Purpose (present)	He works hard so that he may prosper in life.
Wishes and hopes	May Bangladesh long live.
Speculation	They may be waiting at the station for you now.
Give permission (2nd and 3rd person)	You may go now.

3. Could

Past ability/ habitual work	I could walk ten miles at a stretch.
Polite Request	Could you help me?
Past inability	I could not understand you.
Suggestion	You could talk to the Principal.

4. Could have

Someone could do a work but did not do

You could have done the sum.

5. Might

Possibility (less than 'may)	He might leave the country.
Purpose (Past)	He worked hard so that he might prosper in life
Speculation	They might be playing now.

6. Shall

Future event (I,We)	We shall go out for a visit.
Command, threat, Authoritative order (2nd,3rd person)	You shall Carry out my order.
Intention of the speaker	You shall have a nice pen.
Determination	The weak shall be given equal rights.

7. Should

Obligation/Duty	We should obey our parents
Advice/ recommendation	You should stop smoking.
Polite request	Shall I help you?
Use after ‘Lest’	He walked fast lest he should miss the train.
Assumption in present, past and future tense	It should be raining now. He should have reached home by now. He should have much time to reach the station.
Past obligation	He should have read sincerely.

8. Will

Future action	You will do the work.
Future prediction	He will start a school very soon.
Order (2nd and 3rd person)	You will carry out my order.
Determination (1st person)	I will do the work at any cost.
Polite request (2nd person)	Will you post the letter for me?
Future habitual action	Spring will come again.
Conditional	If you want, I will help you.

9. Would

Polite request	Would you post the letter for me?
Offer/invitations	Would you mind having a cup of tea with me?
Purpose( after ‘in order that’ and ‘so that’)	He worked hard in order that he would shine in life.
Conditional (past)	If you wanted, I would help you.
Preference (would rather/would better/would sooner)	He would rather die than beg.

10. Must

Obligation	You must obey your teacher.
Advice	You must take regular exercise.
Logical conclusion	You must be hungry after a long journey.
Certainty	He must be a good boy.
Determination	I must see him punished.
Past certainty	You must have gone there.

11. Have to

Obligation (have to, has to, had to shall have to/ will have to)	I have to look after my old parents.
Indicating advice	You have to learn English.

12. Need

Modal ( need not)	He need not do it.
Principal (need)	He needs to do it.

13. Dare

Modal verb(negative/interrogative)	He dare not do it.
Principal verb (affirmative)	He dared to go there
Challenge	He dares me to do the work.

14. Used to

Discontinued habit	I used to drink tea; now I drink coffee.
Continued habit	Omar (R) used to lead a very simple life.

15. “Be” used as Modal Verb

Duty or necessity (Am to/ is to/ are to)

I am to look after my old parents.

16. Going to

For future intention

They are going to open a bank account.

17. Had better

Preference

You had better go now.