| Function | Time | Form | Example |
| Ability | Present | can is/are able to | She can speak Spanish but she can’t speak Italian. Despite his handicap he is able to drive a car. |
| Past | could was/were able to | Mozart could play the piano at the age of five. Mike’s car broke down but he was able to repair it. | |
| Possibility | Present | may might could | There may be a life on Mars. The rash could be a symptom of something more serious. |
| Past | could have might have | She might have done it; she had an opportunity and the motive. | |
| Future | will be able to | We will be able to travel to the Moon. | |
| Permission | Present/Future | can can’t | “ Can I use your phone?” “No, I’m afraid you can’t ”. |
| Past | was/were allowed to | I was allowed to leave early yesterday. | |
| Obligation | Present | have to must need to should ought to | Students have to wear uniform. I must get up earlier. Do we need to get a visa for the USA? They really should/ought to consult shareholders first. |
| Past | had to | We had to report to Reception by four. | |
| Future | will have to will need to | The Council will have to find ways of cutting costs next year. | |
| Necessity | Present | must have to need to ought to | All human beings must/have to/need to have enough sleep. |
| Past | had to needed to | The staff and the students had to evacuate the campus. | |
| Future | will have to will need to | You will have to/need to work harder than that. |
A. These sentences come from an information booklet about a college. In each case choose the appropriate modal verb: may, must, can, should, be able to, or need.
1) The College welcomes part-time students who… work towards a qualification or attend a recreational education class.
2) Students claiming concessions for tuition fee payments … still pay the registration fees in full.
3) Late entries to examinations … be allowed, but will cost more than entering on time.
4) If you wish to attend a class in English for Speakers of Other Languages, you … take our test before you enroll.
5) If you need any advice, your first point of contact is your tutor, and you … always access other people through him or her.
6) A senior member of staff is on duty each evening between 6.30 and 9.30, and … be contacted via Reception.
7) Students attending evening classes only may not … access all our services. We … however make arrangements for you to see an appropriate adviser during the day.
8) It is regretted that people with physical disability … not be able to take the course that they choose.
9) The Student Council … be elected by students from across the college to represent and promote their general interests.
10) The College café is open from 8.30 am to 4 pm and from 5 to 8 pm. Outside these hours, a range of food and drinks … be purchased from vending outlets.
B. Choose the correct word or phrase to complete each sentence.
1) You must/needn’t save a file before you turn the computer off, or you will lose it.
2) I am afraid this is a non-smoking office, so you don’t have to/can’t smoke in here.
3) Employees are reminded that they mustn’t/needn’t use the office phone to make personal calls.
4) You needn’t/mustn’t send the reminder to Eastwood’s – they paid the invoice this morning.
5) In countries like Iran, you don’t have to/can’t buy or sell alcohol.
6) This income tax form must/needn’t be completed and returned to the Inland Revenue within 30 days.
7) You mustn’t/don’t have to come to the meeting if you have more important things to do.
8) This information is highly confidential, so you mustn’t/needn’t discuss it with anyone.
9) As you are from the European Union, you mustn’t/don’t have to have a visa to go to France.
10) Drivers wishing to hire a car must/can be over 21 and have a full driving license.
C. Look at the chart and make sentences using have to, don’t have to, or can’t.
| obligation | no obligation | prohibition | |
| Airline pilots Union members University teachers Army officers Police officers | have good eyesight pay a subscription be graduates go to training courses be over 1.75m tall | work office hours be qualified teachers carry guns (UK) | drink before flying work during a strike go on strike |
e.g. Airline pilots don't have to have excellent eyesight.
They don’t have to work office hours.
D. Change each of the following sentences using might, can’t, must, and a suitable infinitive.
1) It’s possible that they will give us the discount that we want.
They … might give us the discount we want.
2) Judging by the phone bill, I am sure she has been making long international calls.
Judging by the phone bill, she …
3) The factory is on a 3-day week. I am sure they aren’t selling many cars.
The factory is on a 3-day week. They…
4) It was a very bad deal. I am sure they lost a lot of money.
It was a very bad deal. They …
5) There is a chance she will be promoted at the end of the year.
She …
