This document summarizes the use of modal auxiliaries in English. It discusses modal verbs like can, could, may, might, should, had better, must, will, and would and how they are used to express ability, possibility, permission, advice, necessity, lack of necessity, and prohibition. Examples are provided to illustrate the proper use of each modal auxiliary verb.

1. Modal Auxiliaries

2.  Auxiliary + the simple form of the verb
 Can= I can speak English
 Could= He couldn’t come to class
 May= It may rain tomorrow
 Might= It might rain tomorrow
 Should= Mary should study harder
 Had better= I had better study tonight
 Must= Joe must see a doctor today
 Will=I will be in class tomorrow
 Would= Would you please close the door?

3. EXPRESSING ABILITY: CAN AND COULD
 Can expresses ability in the present or
future
- Bob can play the piano
- You can buy a screwdriver at a hardware
store
The negative form of can may be written :
Can’t, cannot or can not
 The past form of can is could
- Our son could talk when he was two
years old
The negative of could: couldn’t or could

4. EXPRESSING POSSIBILITY: MAY AND MIGHT
EXPRESSING PERMISSION: MAY AND CAN
 May and Might express possibility in the
present or future. They have the same
meaning.
- It may rain tomorrow
- It might rain tomorrow
The negative: may not or might not
 Maybe (spelled as one word) is an adverb
meaning perhaps
- Maybe it will rain tomorrow
- Maybe John is sick
- John may be sick (spelled as two words)
is a verb form may + main verb be

5. ASKING FOR PERMISSION: MAY I, COULD I, CAN I
 People use may I, could I, and can I
to ask polite questions. The
questions ask for someone’s
permission.
- may I please borrow your pen?
- Could I ask you something?
- Can I come to your house tonight?
 Possible answers: Yes, Yes of
course, Yes certainly, Of course,
certainly.
Informal: Sure, Okay, Uh huh

6. ASKING FOR ASSISTANCE: WOULD YOU,
COULD YOU, WILL YOU, CAN YOU
 People use would you, could you, will
you, and can you to ask polite
question. The questions ask for
someone’s help or cooperation.
- Would you please open the door?
- Could you help me please?
- Will you turn the music down? It’s
too loud
- Can you buy something for dinner?

7. POSSIBLE ANSWERS:
Yes, of course
Yes. Certainly
Of Course
Certainly
I’d be happy to
I’d be glad to
Of course I’d be happy to

8. EXPRESSING ADVICE: SHOULD, OUGHT
TO, HAD BETTER
 Should, ought to, and had better
have basically the same meaning.
They mean “this is a good idea, or
this is a good advice”.
 My clothes are dirty I (should/ought to/had
better) wash them
The negative of should is should not
(shouldn’t)
Had better (contraction of had= ‘d)
-You’d better study tonight.

9. EXPRESSING NECESSITY: HAVE TO, HAVE
GOT TO, MUST
 Have to, have got to, and must have
basically the same meaning. They express
the idea that something is necessary.
- I have to/have got to/must study tonight
 Have to is used much more frequently than
must in everyday speech and writing.
 The past form of have to/have got to/must is
had to (meaning necessity).

10. Expressing Lack of Necessity: do not
have to
Expressing Prohibition: Must not
 Don’t/doesn’t have to expresses the
idea that something is not
necessary.
- I finished all of my homework this
afternoon. I don’t have to study
tonight.
- Tomorrow is a holiday, Mary
doesn’t have to go to the class.
 Must not expresses prohibition (DO