Modal Verbs and functions

Overview of Modal Verbs in English

(from Lange, Janet and Ellen Lange. 1999. Writing clearly: An editing guide. Heinle and

Heinle, Massachusetts.)

Modal	Function	Form in the Present	Form in the Past
Can	To show ability	I can run 10 miles.	I could run 10 miles when I was young.
	To suggest a possibility or give an option	Students can pre-enroll in classes.
	To ask for or to give permission	Can you call me? You can leave now.
	To show impossibility	It cannot be Jim standing there. He went away for the weekend.
Could	To show past ability		I could run 10 miles when I was young.
	To ask a polite question	Could I call you?
	To show possibility	Why isn’t Mary here? She could be busy.	Why wasn’t Mary at the party last night? She could have been busy.
	To show impossibility	He could not be here at the party. He is out of town.	He could not have been at the party last night. He was out of town.
	To suggest a possibility/opportunity or give an option	You could try going this way.	You could have tried  going that way.
May	To ask for or to give permission (formal)	May I call you?
	To show possibility	The instructor may come to class late today.	The instructor may have come to class late yesterday.
Might	To show possibility	The instructor might come to class late today.	The instructor might have come to class late yesterday.
Should	To show advisability	You should try the new restaurant downtown.	You should have tried the new restaurant downtown.
	To show obligation	I should renew my driver’s license.	I should have renewed my driver’s license.
	To show expectation	You should receive my letter in two days.	You should have received my letter in two days.
Ought to	To show advisability	You ought to exercise regularly.	You ought to have exercisd regularly.
	To show obligation	I ought to register to vote.	I ought to have registered to vote by October.
	To show expectation	You ought to receive my letter in two days.	You ought to have received my letter two days ago.

Had better	To show advisability	We had better leave. It is getting late.
Must	To show probability or to make a logical assumption	Janice must be out this evening. She does not answer the telephone.	Janice must have been out last evening. She did not answer her telephone.
	To show necessity	I must call my parent tonight.	I was late for the meeting because I had to call my parents last night.
	To show prohibition	You must not cross the street on red light.
Have to	To show necessity	Mike has to make up the class he missed.	Mike had to make up the class he had missed.
	To show lack of necessity	I am glad that I do not have to cook tonight.	I did not have to cook last night.
Will	To indicate future time	He will leave for the plane at 7 a.m.
	To make a promises or to show willingness	The federal government will provide assistance to the hurricane victims.
	To state a general truth	The new car they have developed will run on either gasoline or ethanol.
	To ask a polite question	Will you help me with these boxes?
Would	To ask a polite question	Would you help me with these boxes?
	To indicate a repeated action in the past		When I lived in LA, I would go to the beach every day.
	To indicate future time in the sentence that is in the past		Mark promised that he would help me with my math homework.
Would rather	To show a preference	I would rather go to summer school than graduate late.
Would like	To express a desire	I would like to go to medical school.	I would have liked to go to medical school.