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B2 FIRST · GRAMMAR · PART 4

Modals: obligation and possibility

Must, have to, don't have to, mustn't, be allowed to, had better – and might, be likely to, be bound to.

Finn the puffin with glasses and a book, your grammar teacher
Finn says

Modal verbs are small but powerful: one word can change 'it's necessary' into 'it's forbidden'. Part 4 loves swapping them for longer expressions like 'be allowed to' or 'there's no need'.

Obligation and no obligation

must / have to
= it is necessary
You have to wear a uniform at my school.
don't have to / needn't / there's no need to
= it is not necessary
You don't have to come. = There's no need to come.
mustn't / not be allowed to
= it is forbidden
You mustn't use your phone. = You aren't allowed to use your phone.

Permission and advice

be allowed to / be permitted to
= have permission (permitted is more formal)
Visitors are not permitted to take photos.
let / give someone permission to
let + person + infinitive; give + person + permission to
My parents gave me permission to go.
had better
+ infinitive without to = strong advice
You'd better see a doctor.
should / ought to
= it is a good idea
You ought to apologise.

Ability, offers and suggestions

be able to
= can / could
We weren't able to finish in time.
Shall I…? / Why don't we…?
offers and suggestions
Shall I open the window? Why don't we go to the beach?

How likely is it?

might / may / could
= perhaps
The shop might be closed.
be likely to / there's a chance (that)
= probably / possibly
It's likely to rain. There's a chance we'll win.
be bound to
= certainly
You're bound to love it.

How it comes up in Part 4

In Part 4 you complete the second sentence with the key word, so that it means the same as the first one (2–5 words).

It isn't necessary for you to wear a suit.
NEED
There is no need for you to wear a suit.

Not necessary = there's no need (for someone) to.

Students must not use calculators in the exam.
ALLOWED
Students aren't allowed to use calculators in the exam.

Mustn't = not be allowed to. 'Aren't' counts as two words.

It will probably rain this afternoon.
LIKELY
It is likely to rain this afternoon.

Probably = be likely to + infinitive.

Common mistakes

  • ✗ You mustn't come if you're busy.✓ You don't have to come if you're busy.Mustn't = it's forbidden. Don't have to = it isn't necessary.
  • ✗ You had better to go now.✓ You had better go now.No 'to' after had better.
  • ✗ We are not allow to park here.✓ We are not allowed to park here.Be allowed to – with -ed.
Finn the puffin, smiling kindly
Finn's exam tip

Decide the meaning first: necessary, not necessary, forbidden, allowed, advice or probability. Then check the verb form after the expression: 'had better go', but 'be allowed to go'.

Quick check

Complete the second sentence so that it means the same as the first. Use the key word and write 2–5 words.

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