Modal verbs indicate possibility, probability, ability, permission, obligation or express advice. They include Can, Could, May, Might, Must, Shall, Should, Will, Would.
Modals:
- don't use an 's' for the third person singular.
- make questions by inversion ('she can go' becomes 'can she go?').
- are followed directly by the infinitive of another verb (without 'to').
• PERMISSION
We can use verbs such as 'can', 'could' and 'may' to ask for and give permission. We also use modal verbs to say something is not allowed
- May I ask a question?
- Could I have some tea, please?
- Can we go home now?
• POSSIBILITY or PROBABILITY
We can use these modal verbs when we want to make a guess about something. We choose the verb depending on how sure we are. We can use: must, might, could, may, canorshall.
- They may come by car.
- They might be at home.
- If we don't hurry, we could be late!
• OBLIGATION or ADVICE
We can use verbs such as 'must' or 'should', 'have to', 'could' to say when something is necessary or unnecessary, or to give advice.
- You must stop at a red light
- We have to wear a uniform at work.
- You should send an email.
- You could go by train.
• ABILITY
We use 'can' and 'could' to talk about askill or ability.
- She can speak several languages.
- He can swim like a fish.
- I couldn't see you!