2. The verbs can, could, may, might, must, will,
would, shall, should and ought are
modal verbs.
They do not take a suffix (-s, -ing or -ed).
e.g. He should stay here.
They are followed by a bare infinitive (an
exception is ought which is followed by a to-
infinitive).
e. g. They may come tonight.
You ought to get a job.
3. We use must:
• To express obligation, necessity and
duty.
You must wear a helmet when riding a
motorcycle. (You have to wear a helmet.)
• To express that it is necessary to do
something.
I must water the plants. (It's necessary.)
• For positive logical assumptions. She
must be an actress. I've seen her on TV.
(I'm sure she's an actress.)
4.
5. We use can for ability and can't for a lack of
ability. We can also substitute can with
be able to.
6. We use can't for negative
logical assumptions.
Jack and Paul can't be
strangers. They've been next
door neighbours for years.
(I'm sure they aren't strangers.)
7. We use mustn't /can't for prohibitions.
You mustn't /can't park your car near
a bus stop. (It is forbidden to park
there.)
8. We use have to to express that
it is necessary to do sth
(especially when somebody
else, but not the speaker has
made a decision).
I have to stay late at work
tomorrow. (My boss told me to
stay.)
9. We use don't have to/ needn't
to express lack of necessity.
I don't have to / needn't do the
shopping. I've already done it.
( It isn't necessary for you to do
it.)
10. We use can/ could /may/ might to ask for
permission.
Could /May /Might are more formal than
can.
Can I go to the park?
Could /may/might I take next Monday off?
( Is it permitted for me to…?)
11. We use can / may to give
permission. May is more formal
than can.
Of course, you can use the phone.
You may leave your luggage here,
sir.
(You are allowed to…)
12. We use can't/ mustn't /may not to
refuse permission. May not is formal.
e.g. I'm afraid you can't stay late
tonight.
You mustn't watch TV after 9pm.
You may not cheat during the test.
( You aren't allowed to…)
13. We use could /may /might to
show that something is possible
or likely.
e. g. Tom could/ may /might
still be at school.
(It is possible that he is still at
school.)
14. We use would /could/ can to
make a request.
e. g. Could you open the door
for me, please?
15. We use must / ought to / should
to give advice.
e. g. You ought to / should study more.
You must study better.
