Modals of obligation
Which modal verbs mean that it is necessary to do something?
must, have to
Name three things you can't do until you are 18 years old.
drive, live alone, join the military, work full-time, ...
Which modal verbs mean you are allowed to do something?
can, may
Rewrite the sentence using must:
In most countries, it's essential to wear a seatbelt in a car.
In most countries, you must wear a seatbelt in a car.
Which modal verbs mean you are not allowed to do something? (3)
may not, can't, mustn't
Name two things you are allowed to do in a classroom.
write notes, drink water, ask questions, ...
Complete the sentence so that it has a similar meaning:
It's compulsory for students to wear a tie.
Students ........ (must)
Students must wear a tie.
Complete the sentence so it has a similar meaning:
Making calls in lessons is prohibited.
Students ....... (mustn't)
Students mustn't make calls in lessons.
Is there a difference in meaning?
You can leave your books in the locker.
You may leave your books in the locker.
No.
Complete the sentence so that it has a similar meaning:
We insist that students arrive on time.
Students ..... (have to)
Students have to arrive on time.
Rewrite the sentence using may not:
You do not have permission to talk in the exam.
You may not talk in the exam.
Complete the sentence so it has a similar meaning:
Students have permission to wear rings.
Students ...... (can)
Students can wear rings.
Explain the difference between have to and must.
We usually use must when the speaker has decided that something is important and have to when someone else has decided this. However, in many situations, we can use must and have to in the same way.
Is there a difference in meaning:
You can't eat food in the library.
You mustn't eat food in the library.
They have the same meaning.
Complete the sentence so it has a similar meaning:
We allow students to bring in mobile phones.
Students ..... (can)
Students can bring in mobile phones.