How do modal verbs work

2. What is a modal verb?
A modal verb (also modal, modal auxiliary
verb, modal auxiliary) is a type of auxiliary
verb that is used to indicate modality – that is,
likelihood, ability, permission, and obligation.
YOU MUSTN’T EAT HERE
YOU MUSTN’T TO EAT HERE

3. The MODAL verbs you need to know in
unit 3 are:
COULD, MANAGED TO, CAN, WILL BE ABLE TO
MAY/MIGHT/COULD, MUST, CAN’T
SHOULD, MUST, HAVE TO

4. ABILITY AND ACHIEVEMENT:
COULD, MANAGED TO, CAN, WILL BE ABLE TO
Before the 19th century, doctors could operate, but without anaesthetic (general
ability in the past)
Scientists managed to clone an animal in the 1990s (specific achievement in the
past))
Surgeons can now transplant human faces (present ability)
In the future we will probably be able to transplant brains (future ability)

5. Complete the text with positive and negative forms of
can, could, managed to and will be able to
Boy in a bubble
When Rob Thompson was born, he had a defective immune system. Doctors
________ save his life, but for years, he ______
Only survive inside a sterile plastic bubble or room. He ______ go outside or
play with friends. Later, scientists _________ develop a new gene treatment
for people like Rob. Thanks to this treatment, Rob _______now do most of
the things that a normal
Child can do, although he _______live without special drugs. In the future,
scientists _______help other children with gene therapy. One day people like
Rob ____live normal lives.

6. POSSIBILITY AND CERTAINTY:
may/might/could, must, can’t
Your doctor may (not) ask you to give up smoking (possibility)
That new medicine might (not) cure you (remote possibility))
It could be more effective for some skin problems (possibility)
The stings must be painful (certainty)
Zootherapy can’t be a fraud, I’m sure it works! (certainty)
It may rain tomorrow. I may ask you to drive me to work. It might snow, but I don’t
think it will. It could rain heavily, that’s all. It must be dangerous to drive in the snow.
It can’t be true. No, I don’t think it will snow.

7. Choose the correct alternative
James isn’t at school today. He ____ be ill.
a) can’t b) may c) may not
Sarah’s brother had a car accident. She ___be worried.
a) must b) might c) can’t
The children aren’t eating their vegetables. They
___like them.
a) can’t b) must c) might not

8. ADVICE AND OBLIGATION:
should, must, have to
You should give up eating between meals (advice)
We must cut down on fatty foods (obligation)
You don’t have to go without fast food (absence of obligation)
You shouldn’t eat so many of them (advice)
You mustn’t stay in class during the break (prohibition)
You have to get out more (obligation)

9. Complete the sentences with the correct form of
the verbs from the box
don’t have to must mustn’t shouldn’t have to should
0. If you want to learn how to swim, you should take lessons
1. You _______smoke in restaurants and cafés now –it’s illegal.
2. I _______buy a train ticket before I forget.
3. During the holidays, I ________go to school.
4. You ______go to bed late on a school night.
5. ______ you_______ study tonight?

10. PAST MODALS: possibility and
certainty
It may have been a virus (we think this possibly happened/didn’t happen)
It can’t have done you any good (we think this definitely didn’t happen)
That could have helped him a lot (we think this possibly happened/didn’t
happen)
She must have exercised every day (we think this definitely happened)
The burger might not have made you sick (we think this possibly happened/didn’t
happen)

11. Choose the correct option:
- Sian can’t / must have been at school today because she didn’t
come to English or Biology.
- I suppose she could / can have been ill.
- Maybe. But her mum’s just had an operation so she can’t /
might have been at the hospital.
- Well, I saw her mum in the car yesterday so she must / could
have already come home.