Modal Verbs

Modal Verb

Expressing

Example

MUST

• 100% obligation

I must stop when the traffic lights turn red.

• Imperative / insistent advice or invitation

You must read this book. It's much spoken about and is worth reading.

• Prohibition (negative)

You must not smoke in the hospital.

• Unwillingness, reluctance; irritation (interrogative)

Must I get up that early on Sunday?

Have (got) to

• Induced/ forced  necessity

It's getting late and I've got to go home.

I had a lot of work to do, so I had to sit up late.

He'll have to stay in bed for some time - he is getting down with a cold.

CAN

• Ability
• Ability in the past (Could)

Can you swim?

When I was younger I could stay up all night and not get tired.

• Possibility

Smoking can cause cancer !

• Request (interrogative)
• Asking for and giving permission (informal)

Can you give me your book for a while?

Can I use your phone please?

Can I help you?

Now that we have finished the work you can go home. (I allow you to go home)

To be able to

• Ability in the future

I 'm afraid I won't be able to come to see you tonight.

COULD

• Permission/ request (more polite)

Excuse me, could I just say something?

Could you, please ...

MAY

• Asking for permission (formal)

May I use your phone please?

May I come in?

SHOULD/ OUGHT to

• 50% obligation

I ought to/ should see a doctor. I have a terrible headache.

• Advice, rcommendation

You should spend more time in the open.

• Reproach (+ Perfect Infinitive)

You should have informed me yesterday that you wouldn't come today!

Had better

• Advice

You had (You'd) better stay at home in such nasty weather.

SHALL

• Offering to do smth or suggesting (doing) smth
• Asking for advice or instructions (interrogative)

Shall I open the window?

Shall we meet at 6?

I've lost my bag. What shall I do?

NEED

• Necessity              

Need I say that I love you!?

• Lack of necessity /

absence of obligation (negative)

I need not buy any tomatoes. There are plenty of them in the fridge.

You needn't call him. I'll do it myself