Modals: permission and obligation

Do you know how to use modal verbs to talk about permission and obligation? Enhance your knowledge with a lesson given below and the grammar explanation to guide you better.

Look at these examples to see how can, can't, must, mustn't, have to, and don’t have to are used.

• You can park your car in the garage.

• You can't bring pets into the restaurant.

• I must send this package before the post office closes.

• You mustn't touch the stove when it's hot.

• You have to show your ID to enter the building.

• You don’t have to pay for the museum entry; it's free on Sundays.

Grammar explanation - Modals: permission and obligation

We often use verbs with modal meanings to talk about permission and obligation.

1. Permission

a) Can

We often use can to ask for and give permission.

• Can I open the window?

• You can borrow my umbrella if you need it.

• Can I offer some advice?

b) Could

We also use could to ask for permission (but not to give it). Could is more formal and polite than can.

• Could I ask for a glass of water?

• Could I step outside for a moment?

• Could I use your charger, please?

c) May

May is the most formal way to ask for and give permission.

• May I enter the meeting room?

• Staff may take breaks at designated times.

• May we use your conference room for a presentation?

d) Prohibition

We use can't and mustn't to show that something is prohibited – it is not allowed.

e) can't

We use can't to talk about something that is against the rules, particularly when we didn't make the rules.

• You can't bring food into the library.

• He can't enter the building without a badge.

• We can't swim in this part of the river.

f) must not / mustn't

We use must not to talk about what is not permitted. It is common on public signs and notices informing people of rules and laws.

• Employees must not use personal devices during working hours.

• You must not touch the paintings in the gallery.

• Children must not run in the hallways.

We use mustn't particularly when the prohibition comes from the speaker.

• (Parent to child) You mustn't talk back to your elders.

• (Coach to team) You mustn't skip practice without telling me.

• I mustn't forget to send that email today.

2. Obligation

We use have to and must to express obligation. There is a slight difference between the way we use them.

a) have to

Have to shows us that the obligation comes from outside the speaker.

• We have to submit the report by Friday.

• (Student to teacher) When do we have to turn in our assignments?

• She has to attend the meeting later today.

We sometimes call this 'external obligation.'

b) Must

Must expresses a strong obligation or necessity. It often shows us that the obligation comes from the speaker (or the authority that wrote the sentence).

• I must finish this project before the deadline.

• (Boss to employee) You must complete the training by the end of the week.

• (Notice) Helmets must be worn in this area.

Note that we don't use must to express obligation in the past. We use have to instead.

• I had to wake up early for a conference yesterday.

3. No obligation

a) don't have to

We use don’t have to to show that there is no obligation. You can do something if you want to but it's not compulsory.

• You don't have to dress formally for the dinner, but you can if you'd like.

• You don't have to wait in line. You can go straight in.

• You don't have to come with us if you're tired.

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