auxiliaries verbs.
When are modal verbs used?
Modal verbs are used to express functions such as:
Advice
- You should / ought to revise your lessons
Ability
- She can speak six languages.
- My grandfather could play golf very well.
- I can’t drive.
Command
- You must wash your hands before cooking.
- You need to be here before 8:00.
Habits
- When I lived in Italy, we would often eat in the restaurant next to my flat.
- John will always be late!
Lack of necessity
- I need not buy tomatoes. There are plenty of tomatoes in the fridge.
Likelihood
- Her parents must be so proud.
- My baby brother should be asleep by now.
Obligation
- Children must do their homework.
- We have to wear a uniform at work.
- You should stop smoking.
Permission
- Could I leave early today, please?
- You may not use the car tonight.
- Can we swim in the lake?
Prohibition
- You must not smoke in the hospital.
Possibility/Probability
- It may rain tomorrow!
| MODAL VERB | EXPRESSING | EXAMPLE |
|---|---|---|
| must | Strong obligation | You must stop when the traffic lights turn red. |
| logical conclusion / Certainty | He must be very tired. He’s been working all day long. | |
| must not | prohibition | You must not smoke in the hospital. |
| can | ability | I can swim. |
| permission | Can I use your phone, please? | |
| possibility | Smoking can cause cancer. | |
| could | ability in the past | When I was younger I could run fast. |
| polite permission | Excuse me, could I just say something? | |
| possibility | It could rain tomorrow! | |
| may | permission | May I use your phone, please? |
| possibility, probability | It may rain tomorrow! | |
| might | polite permission | Might I suggest an idea? |
| possibility, probability | I might go on holiday to Australia next year. | |
| need not | lack of necessity/absence of obligation | I need not buy tomatoes. There are plenty of tomatoes in the fridge. |
| should/ought to | 50 % obligation | I should / ought to see a doctor. I have a terrible headache. |
| advice | You should / ought to revise your lessons | |
| logical conclusion | He should / ought to be very tired. He’s been working all day long. | |
| had better | advice | You’d better revise your lessons |