Modal auxiliary verbs such as can, must and will allow us to express concepts such as “ability” and “obligation”. We also use them to allow us to perform a wide range of functional tasks, such as making requests or speculating. The context in which modal verbs appear is important as each modal has a number of different uses.
Some modals do not have a future or past form.
We can´t use two modals together.
1) Can (infinitive to be able)
We use can
- To talk about abilities:
She can skate beautifully.
- To ask for permission:
Can I borrow your dictionary?
- For requests:
Can you lend $10?
ü Remember:
The infinitive form of can is to be able to:
I may be able to attend.
The simple past of can is could or was/were able to:
He could drive before the accident. / He was able to drive before the accident.
2) Could
As well as being the past form of can we use could
- To discuss alternatives and opinions:
We could invite everyone to a restaurant, or else we could have a picnic on the beach.
- To make more polite requests:
Could you bring me the bill, please?
Could you speak a little more slowly, please?
- We use can for speculating, guessing and discussing possibilities:
The weather could be better tomorrow. (It´s possible)
- Could or was able to
- We use could to talk about general past abilities
He could run for miles when he was younger.
However, if we want to say we succeeded in doing something on a particular occasion, or after a lot of difficulty we use be able to:
I drove around for forty minutes, finally I was able to find somewhere to park.
3) Must
We use must
- For orders we give to ourselves:
I must pay the phone bill, otherwise they will cut me off.
- To prohibit something (used in mainly written rules and regulations):
You mustn´t speak on your mobile when you´re driving.
ü Remember
Non-native speakers can over-use must. It can sound rude or aggressive. To give orders, or to describe duties use have to instead. Make polite requests with could you? instead.
- For a strong recommendation:
You must see the new James Bond film, it´s wonderful.
- For making intelligent guesses and deductions:
She must be Melanie´s twin sister. They are almost identical.
- For deductions in the past we use must have been / can´t have been:
He must have been disappointed not to pass. His teacher can´t have been pleased either.
- For negative deductions we use can´t be, not mustn´t be:
My parents want me to revise all weekend – they can´t be serious! (NOT: They mustn´t be serious.)
4) Have to
We use have to:
- To talk about our duties or obligations
I have to deal with phone calls and enquiries and give advice to students.
- To show that something isn´t obligatory or necessary:
You don´t have to bring a dictionary to school, we have one in every classroom.
5) May
We use may:
- To talk about possibility
It may rain this afternoon.
- To ask for permission
May I use your phone?
ü Remember
“May I” is generally considered more polite than “Can I”.
6) Might
We use might
- To express a more remote possibility than may, and to speculate.
It might be difficult to get a baby-sitter.
- As a very polite or formal way of asking for permission, or making a request
Might I say something here?
Might I borrow your phone book for a minute?
7) Will
We use will
- For making predictions and talking about the future
- When we make offers or decisions as we speak
Leave the washing up. I´ll do it later.
Q: Can someone answer the door?
A: I´ll go.
- To talk about habitual actions
Most days, I´ll normally take the 7:42 train to Marylebone.
- To make requests or give orders
Will you drop me off in front of the bus station, please?
ü Remember
Shall can sometimes be used instead of will.
In informal, or more old-fashioned English, when the subject of the modal is I or we, we can use shall, although this is quite rare.
I shall give you my decision in the morning.
Shall is more commonly used with I and we for offers, or to ask for suggestions.
Shall I answer the phone?
What shall we do tonight?
Shall we go to the cinema?
8) Would
We use would
- To make polite requests
Would you look after my bag for a few minutes?
- In conditional sentences
- In reported speech as the reported form of will
He said he would help me, but he didn´t.
- To talk about past habits
When we were young we would sit on that old bench near the entrance to the park.
9) Should and ought to
We use should and ought to
- To give advice
You should/ought to be more careful about what you say in front of her, she repeats everything.
- To say what we think is morally right.
Rich countries should help developing countries.
- To criticise a past action
You should have made sure that tickets were in the bags.
You shouldn´t have been so greedy.
We tend not to use oughtn´t to/oughtn´t to have as it is too hard to say.
- To make predictions based on previous experience, or what is expected.
Don´t panic, there should be another bus in a couple of minutes.
10) Need
We use need
- To say when something is necessary or unnecessary.
We need to enroll everyone for the exam before the deadline.
We use needn´t to (don´t need) to say that something is not necessary:
You needn´t buy/ don´t need to buy uniforms and equipment, everything is included in the fees.
ü Remember
Need can be used both as a modal auxiliary, and as a full verb with an auxiliary. This can be used to make an important distinction of meaning in the past.
Need as a modal: I needn´t have worn a suit because everyone was dressed casually = I wore a suit, but it wasn´t necessary.
Need as a full verb: I didn´t need to wear a suit, so I just dresses casually like everyone else.
Need as a modal: I needn´t have bought the tools because the company supplied everything = I bought the tools but it wasn´t necessary.
Need as a full verb: I didn´t need to buy any tools because the company provided everything = it wasn´t necessary to buy any tools so I didn´t.
