We often use modal verbs or other modal expressions when we want to express an opinion or attitude about a possible fact or to control a possible action. All modal expressions are about the speaker’s or writer’s view of the world.
He’s her brother. She told me.
I know this fact for certain. I am not expressing an opinion about it. I am stating it as a fact.
He must be her brother. They look so much alike.
I am expressing an opinion about a fact because of the evidence that I have.
Jan always goes with us.
I’m not expressing an attitude or opinion about this action.
OK. Jan can go if she’s finished.
I’m controlling a possible action. I’m giving Jan permission.
We can divide most modal words and expressions into two types of meaning:
The speaker or writer decides how certain something is, either in the present, future or past. They predict or speculate about a fact. We see this type of meaning when we talk about degrees of certainty, possibility, likelihood, doubt:
Paula can’t be home yet. It’s impossible. She left 10 minutes after us.
[The speaker hears the phone ring and predicts who is ringing.]
There’s the phone. That’ll be Mum.
I may go. I haven’t decided yet.
The speaker or writer wants to control or ‘direct’ the action. They give and refuse permission. They talk about obligation and necessity. They talk about how they would like the world to be:
[parent says to child]
You can come if you’re good.
He should take more care.
Tell Jen she needn’t bother about the washing up.
You mustn’t worry so much about her.
You may go now. (formal)
Often the same modal verb is used to express different meanings.
My birthday will be on a Monday this year.
I won’t have a party.
I shall have plenty to tell you when I see you.
I shan’t ask you to come again.
The cakes must be ready soon. They’ve been in the oven for an hour.
You can’t be hungry. You had a huge lunch.
The traffic isn’t heavy. We should be there in an hour.
The traffic isn’t heavy. We ought to be there in an hour.
She may be a friend of Richard’s.
She might be a friend of Richard’s.
She could be a friend of Richard’s.
You must arrive at 6 to pick up the tickets.
I have to go up to the hospital twice a week.
We need to win this game to get into the final.
Children should look after their parents in old age.
Children ought to look after their parents in old age.
I needn’t do it now. I’ll do it later.
don’t need to
I don’t need to do it now. I’ll do it later.
don’t have to
I don’t have to do it now. I’ll do it later.
Can we go out now?
You can go now if you’ve finished.
You may go now if you’ve finished.
May I borrow a chair?
Could we borrow the car?
Might we have a little more time to finish the exam? (very formal)
You can’t go in without a ticket.
You may not enter while the exam is in progress. (formal)
You must not leave your bike in front of the fire exit.
I’ll get it. You stay there.
Shall I go and make dinner?
Will you close that door?
Would you close that door?
Could you help me with this?
I’ll come back before 6.
I think I’ll eat later. I’m not hungry now.
advice and suggestion
You should apply for that job.
Can you swim underwater?
I could play much better ten years ago.
Too much exercise can be bad for you.
A list of verbs may be found at the back of the book.