UNITS 4 & 5

MODALS

The modal verbs are:

can	could
may	might
shall	should
will	would
must

We use modal verbs to show if we believe something is 
-certain, 
-probable or -
possible (or not). 
We also use modals to do things like talking about 
-ability, 
-asking permission,
- making requests and offers, and so on.

Possibility:

We use the modals could, might and may to show that something is possible in the future, but not certain:

They might come later. (= Perhaps/Maybe they will come later.)
They may come by car. (= Perhaps/Maybe they will come by car.)
If we don’t hurry we could be late. (= Perhaps/Maybe we will be late)

We use the modal can to make general statements about what is possible:

It can be very cold in winter. (= It is sometimes very cold in winter)
You can easily lose your way in the dark. (= People often lose their way in the dark)

We use the modal could as the past tense of can:

It could be very cold in winter. (= Sometimes it was very cold in winter.)
You could lose your way in the dark. (= People often lost their way in the dark)

Impossibility:

We use the negative can’t or cannot to show that something is impossible:

That can’t be true.
You cannot be serious.

We use couldn’t/could not to talk about the past:

We knew it could not be true.
He was obviously joking. He could not be serious.

Probability:

We use the modal must to show we are sure something to be true and we have reasons for our belief:

It’s getting dark. It must be quite late.
You haven’t eaten all day. You must be hungry.

We use the modal should to suggest that something is true or will be true in the future, and to show you have reasons for your suggestion:

Ask Miranda. She should know.
It's nearly six o'clock. They should arrive soon.

Ability:

We use can to talk about someone’s skill or general abilities:

She can speak several languages.
He can swim like a fish.
They can’t dance very well.

We use can to talk about the ability to do something at a given time in the present or future:

You can make a lot of money if you are lucky.
Help. I can’t breathe.
They can run but they can’t hide.

We use could to talk about past time:

She could speak several languages.
They couldn’t dance very well.

Permission:

We use can to ask for permission to do something:

Can I ask a question, please?
Can we go home now?

could is more formal and polite than can:

Could I ask a question please?
Could we go home now?

may is another more formal and polite way of asking for permission:

May I ask a question please?
May we go home now?

We use can to give permission:

You can go home now if you like.
You can borrow my pen if you like.

may is a more formal and polite way of giving permission:

You may go home now, if you like.

We use can to say that someone has permission to do something:

We can go out whenever we want.
Students can travel free.

may is a more formal and polite way of saying that someone has permission:

Students may travel free.

Instructions and requests:

We use could you and would you as polite ways of telling or asking someone to do something:

Could you take a message please?
Would you carry this for me please?
Could I have my bill please?

can and will are less polite:

Can you take a message please?
Will you carry this for me please?

Suggestions and advice:

We use should to make suggestions and give advice:

You should send an email.
We should go by train.

We use could to make suggestions:

We could meet at the weekend.
You could eat out tonight.

We use conditionals to give advice:

Dan will help you if you ask him.

Past tenses are more polite:

Dan would help you if you asked him.

Offers and invitations:

We use can I… and to make offers:

Can I help you?
Can I do that for you?

We can also use shall I …

Shall I help you with that?
Shall I call you on your mobile?

We sometimes say I can ... or I could ... or I’ll (I will) ... to make an offer:

I can do that for you if you like.
I can give you a lift to the station.
I’ll do that for you if you like.
I’ll give you a lift to the station.

We use would you like (to) ... for invitations:

Would you like to come round tomorrow?
Would you like another drink?

We use you must or we must for a very polite invitation:

You must come round and see us.

We must meet again soon.

Obligation and necessity

We use must to say that it is necessary to do something:

You must stop at a red light.
Everyone must bring something to eat.
You can wear what you like, but you must look neat and tidy.
I’m sorry, but you mustn’t make a noise in here.

We use had to for this if we are talking about the past:

Everyone had to bring something to eat.
We could wear what we liked, but we had to look neat and tidy.

Must vs. have to 
Both Must and have to express obligation or necessity, but there are some small differences: 

•  Must expresses the speaker's feelings, whereas have to expresses, above all, an impersonal idea:

You must come. You are obliged to come (I require that you come)
You have to come. You are obliged to come. (There's a rule requiring you to come)

Must I wear this tie? Am I obliged to wear this tie? (What do you think?)
Do I have to wear this tie? Am I obliged to wear this tie? (Is there a rule about ties?)

•  Have to mainly expresses general obligations, while must is used for specific obligations:

I have to brush my teeth twice a day.

I must tell you something.

Important: To express obligation, duty or necessity in the future or the past, must and need are not used. They are replaced by have to:

We must (need to) buy another ticket.
We had to buy another ticket yesterday.
We'll have to buy another ticket later.

However, in their negative forms, mustn't and don't have to have completely different meanings: 

•  Mustn't expresses prohibition

You mustn't drive. You are prohibited to drive. You are not allowed to drive.

•  Don't have to expresses the absence of obligation or necessity:

You don't have to drive. You are not obliged to drive (but you can if you want to).

BE ALLOWED TO

Use: to say what you can/can’t do.

We aren’t allowed to smoke in the office. (= We can’t smoke in the office).

We are allowed to smoke in the office. (= We can smoke in the office).

Past tense: was/were allowed

We were allowed to smoke in the office.

Modals of deduction present from hacersivil

Exercise 1
Exercise 2
Exercise 3
Exercise 4
Exercise 5

Future forms presentation from hacersivil