Modal Verbs And The Functions

Modal verbs are special verbs (like must, have to, can, would, etc) which have certain function. Modals or modal auxiliary verbs are used to give the additional information or explanation about the function of the main verb that we use in a sentence. Modals have special characteristics.


They never change their form and they are always followed by infinitive without "to". For example, we use "would go" not "would to go". Commonly, modal verbs are used to express certainty, possibility, willingness, obligation, necessity, and ability.

Modals and Their Functions

Modal	Function : to express	Example
Must	certainty conclucion	That man has a lot of expensive cars. He must be very rich.
	strong obligation	Children must obey their parents.
	prohibition	You must not smoke here!
Should/ ought to	logical conclusion	He should be tired. He's been doing his homework all night long.
	obligation	You ought to start working at once.
	advice or tips	I think you should go to hospital.
Had better	strong advice	We had better hurry because we're almost late.
Can	ability	He can answer these questions.
	possibility	Smoking can cause cancer.
	permission	You can go home now.
Could	ability in the past	When he was ten, he could answer these questions.
	possibility	If you want, we could go to the movies.
	polite permission	Could I say something?
May	permission	May I use your computer?
	possibility, probability	She may be too busy to help you right now.
Might	polite permission	Might I use your computer?
	possibility, probability	You might become president one day.
Will	invitation, request	Will you come in, please?
	logical possibility	As a result, the market will close earlier than usual today.
Would	will in past	He said he would celebratehis birthday at home.
	polite demand, invitation	Would you sit down, please?

We can also classify modal verbs according to their functions.

Use	Explanation	Modal in example
Logical possibility	strongest	Anne looks very relaxed. She must know the answers to all these questions.
	stronger	As a result, Mr. president will go to South Sumatera earlier than the schedule.
	strong	This aplication would not work well everyday.
	strong	He should be tired. He's been working all day long.
	strong enough	He may be too busy to help you right now.
	weak	Smoking can cause impotent.
	weak	If I have spare time, we could go to the movies.
	weak	They might have nothing to do at the moment, but I'm not sure.
Obligation	strong	Everybody must wear a uniform at the ceremony.
	weak (50%)	You should go to your grandmother's home.
Permission	most polite	May I borrow your magazine?
	polite	Could I use your pen? I don't see mine.
	impolite	Can I use your computer?
Ability	Strong	She can answer all these questions.
	weak	I could easily jump over the wall when i was younger.