Must and Have to for Strong Obligation

Both words must and have to are used to indicate a strong obligation. In the affirmative form, have to has the same meaning as must and is used to express obligations. However,  have to is much more flexible than must because we can use it in the past, the present and the future. For this reason it is very commonly used in modern English. Must is used in official documents: Passengers must keep their bags with them at all times.

Level A2/B1

Difference Between Must and Have to


  • Must indicates an internal need or obligation: My tooth is sore. I must go to the dentist.
  • Must is is also used to say that we are quite sure that something is true: They are almost identical. They must be sisters.
  • Have to indicates an external need or obligation:  To travel, you have to carry a passport.

Although this is the guiding rule, there are so many exceptions to it that it is a weak rule. The rule should be applied. You should be prepared for plenty of examples that go against it.


  • Must is a modal verb and is used in formal, written language: Students must prepare for their classes.
  • Have to is more often used in conversations: I have to do lots of home assignments.


  • Must is only used in the present tense: I must do housework.
  • Have to can be used in the past and future: I have to tidy my room. I had to tidy my room yesterday. I’ll have to tidy my room tomorrow.

Have Practice in Using Modal Verbs Must and Have to

Exercise 1. Complete the sentences with must or have to

  1. The bus goes at 10.15. She __________ leave at 10 if she wants to catch it.
  2. The British Library: Coats and bags __________ be left at the coakroom or in a locker.
  3. Jim can’t see very well. He __________ wear glasses.
  4. You __________ see the film. It’s fantastic.
  5. Johny, you __________ be nice to your mum.
  6. Oh, no. It’s Monday tomorrow. I __________ go to school again.
  7. English children __________ stay at school till they are 16.
  8. OK. You can go to the party, but you __________ be back before midnight.
  9. A flight attendant: “All mobile phones __________ be switched off during the takeoff.”
  10. The metro station is closed. I __________ get a taxi.

Exercise 2. Complete these sentences with must, mustn’t or the correct or the correct form of have to.

  1. At our school we __________ wear a uniform.
  2. You __________ cross the roads without looking. It’s dangerous.
  3. You _______ turn on the central heating. It’s automatic.
  4. The exams are next week. I __________ work harder.
  5. You ________ forget your umbrella. It’s going to rain.
  6. Students _________ listen to the teacher or they won’t understand.
  7. You _____ cross the road when the red light is showing.
  8. We __________ leave now or we’ll miss the plane.
  9.  Soldiers ____________ obey orders.
  10. Sorry, I ___________ go now. I don’t want to be late.
  11. Shop assistants __________ deal with the public.
  12. You __________ come with us if you don’t want to.
  13. I was late this morning because I _________ wait a long time for the bus.
  14. In Spain, teachers __________ wear uniforms.
  15. You ___________ take food in your room.
  16. You __________ use the elevators in case of fire.
  17. I _________ wear glasses because I can’t see very well.
  18. You ___________ read this book. It’s really good.
  19. You __________ go shopping today. We don’t need anything.
  20. You __________ a mobile phone in class.
  21. We ___________ feed the animals. It’s forbidden.
  22. We _________ book the tickets before it’s too late.
  23. In Spain, teachers _________ work on Saturdays.
  24. In Britain you __________ drive on the left.
  25. Every player in a football team __________ have a number.
  26. You ___________ forget his birthday again.
  27. Doctors sometimes ___________ work at the weekend.
  28. Nowadays in Spain pupils ____ learn Latin at school.
  29. You __________ smoke on public places.
  30. My wife __________ go to work today. It’s a holiday.
  31. You _________ shout. I can hear you.
  32. We ___________ be quiet in the library.
  33. You __________ use a computer on the plane.
  34. She ___________ come to the dentist’s with me.
  35. At a restaurant you _________ pay the bill but you __________ eat everything.

Exercise 3. Must and Hve to. Choose the correct answer from ​A​, ​B​, ​C​ and ​D​.

1. Everyone __________ the law.

A. must obeys ​
B. must to obey​
​C. must obey ​ ​
D. must obeying

2. The film is excellent. You __________ see it.

A. must to​ ​
B. must ​
C. will must​
D​ . must have to

3. You must __________ over 18 to drive a car.

A. to be​
​B. be​ ​
C. will be​ ​
D. are

4. You __________ in this room.

A. mustn’t to smoke
​B. must no smoking
C​ . mustn’t smoke ​
D. must to smoke

5. This is a library. We __________ quiet.

A. must be ​ ​
B. must to be ​
C. mustn’t be ​ ​
D. must being

6. Tomorrow, I __________ finish the work.

A. will must ​
B. must will​ ​
C. will have ​
D. must

7. She is very ill. She __________ in bed.

A. must stays​ ​
B. must to stay ​
C. must staying ​
D. has to stay

8. I’ve got toothache. I __________ see the dentist tomorrow.

A. will must​
​B. must will ​
C. have to​ ​
D. must be

9. He __________ his sister.

A. must helps​ ​
B. must be help ​
​C. must help​
​D. must have to help

10. It’s early! __________ go?

A. Do you must​ ​
B. Must you have to​
​C. Have you to​ ​
D. Must you

Exercise 4. Make questions or negative sentences using ​have to​. Use present, future or past forms.

  1. Is it necessary for you to study? – ______________________________________ study?
  2. It isn’t necessary for him to go to school. – He ______________________________________ school.
  3. Is it necessary for her to help her parents? – ______________________________________ her parents?
  4. Must we wait? – ______________________________________ wait?
  5. Will it be necessary for them to take the exam? – Will  ______________________________________ the exam?
  6. Was it necessary for you to pay for the tickets? – ______________________________________ for the tickets?
  7. Was it necessary for them to go to London? – ______________________________________ to London?
  8. It wasn’t necessary for them to help their mother. – ______________________________________ their mother.
  9. Must the twins stay at home? – ______________________________________ at home?
  10. Must you wear a uniform at your school? – ______________________________________ at your school?

Exercise 5. Must and Have to. Look at these situations. Write a sentence for each using ​mustn’t,​ ​must​ or ​don’t/doesn’t have to​.

  1. Don’t walk on the grass. You ______________ on the grass.
  2. Don’t smoke in this building. You ______________ in this building.
  3. You can go inside without a ticket. You ______________ buy a ticket.
  4. The film is very good. See it! You ______________ the film.
  5. You can work here without knowing English. You ______________ know English.
  6. It’s OK if you don’t want to help me. You ______________ help me.
  7. Don’t touch the paintings. You ______________ the paintings.
  8. It’s not compulsory for him to go to school. He ______________ to school.
  9. You have to wash the dishes. You ______________ the dishes.
  10. This is very good champagne. Drink some. You ______________ some of this champagne.

Exercise 6. Rewrite the sentences with can, may, must or have to

Example: Is that all right if I borrow your pen? – May/Can I borrow your pen?

  1. Don’t park your car on bends. It is illegal. You ______________ your car on bends. It is illegal.
  2. Perhaps she will agree with it. Who knows? She ______________ with it. Who knows?
  3. Our teacher asked us to tidy the classroom. We ______________  the classroom.
  4. I need your help. It’s too much work for me. You ______________ me. It’s too much work for me.
  5. Look at that balloon. It’s over there. ______________ you see that balloon? It’s over there.
  6. Don’t worry about dinner. I’ll make it. You ______________ about dinner. I’ll make it.
  7. It is not necessary to be there. We ______________ there.
  8. Why don’t you stay with us? No problem! You ______________ with us. No problem!

Exercise 7. Fill in the blanks using MUST, MUSTN’T, DON’T HAVE TO, SHOULD, SHOULDN’T, MIGHT, CAN, CAN’T

  1. Rose and Ted _________________ be good players. They have won hundreds of cups!
  2. You _________________ pay to use the library. It’s free.
  3. I’m not sure where my wife is at the moment. She _________________ be at her dance class.
  4. Jerry _________________ be working today. He never works on Sundays.
  5. You _________________ be 18 to see that film.
  6. You _________________ hear this story. It’s very funny.
  7. Dad _________________ go and see a doctor. His cough is getting worse all the time.
  8. You don’t have to shout. I _________________ hear you very well.
  9. It _________________ be him. I saw him a week ago, and he didn’t look like that.
  10. You look pretty tired. I think you _________________ go to bed early tonight.
  11. Let me look. I _________________ be able to help you.
  12. “Children, you _________________ cross the street if the lights are red!”
  13. You _________________ sit so near the TV. It’s bad for your eyes.
  14. I’m sorry but I _________________ give you a lift because my car is broken.
  15. I _________________ stop and talk to you now. I have to get to the library.
  16. You really _________________ go to the Louvre if you’re in Paris. It’s wonderful.
  17. You _________________ come to the party if you don’t feel well.
  18. I don’t know where Kelly is. She _________________ be at her sister’s.
  19. You have passed all your tests. You _________________ be very pleased with yourself.
  20. You _________________ smoke in your car, especially if there are children sitting in the back.
  21. You _________________ work this evening. I can do the tasks for you.
  22. John doesn’t need a calculator. He _________________ do sums in his head.
  23. Passengers _________________ open the door when the train is moving.
  24. It _________________ rain today. It’s getting cloudy already.
  25. I _________________ pay for the tickets because I got them from Sam for free.

Use must and have to in your own sentences.