MODALS VERBS

MODALS VERBS OF OBLIGATIONS

We can use have to + infinitive, must + infinitive and should + infinitive to express obligation (something you have to do).

Present	Positive	Negative
have to / don't have to	strong obligation (possibly from outside) Children have to go to school. (sometimes 'have got to')	no obligation I don't have to work on Sundays. You don't have to eat anything you don't like.
must / mustn't	strong obligation (possibly based on the speaker's opinion) I must study today.	negative obligation You mustn't smoke here.
should / shouldn't	mild obligation or advice You should save some money.	mild negative obligation or advice You shouldn't smoke so much.

Be careful about the difference between mustn't and don't have to!
Mustn't means it's not allowed, or it's a bad idea:

• You mustn't eat so much chocolate, you'll be sick

Don't have to means you don't need to do something, but it's fine if you want to do it:

• I don't have to get up early at the weekend(of course, if I want to get up early, that's fine, but I can stay in bed if I want).

Past	Positive	Negative
had to / didn't have to	obligation in the past I had to wear a school uniform when I was a child.	no obligation in the past We didn't have to go to school on Saturdays.
must*	changes to 'had to'	-
should have + pp / shouldn't have + pp	a past action which didn't happen: the advice / regret is too late You should have gone to bed earlier, now you have missed the train.	a past action which didn't happen: the advice / regret is too late You shouldn't have taken that job., it was a bad idea.

* Remember 'must have done' is a modal verb of deduction or speculation, not obligation in the past. For example: Julie must have left. Her coat's not here. See modals of probabilty for more information.

• Click here for modal verbs of obligation exercise 1
• Click here for all the modal verbs exercises

LET´S PRACTICE

READING AND PRACTICE 

The deadline 

Maggie: Hi Tom, have you finished your homework? 

Tom: Oh hi Maggie. No, I haven’t. 

Maggie: The deadline is tomorrow you know so you have to submit it tomorrow. 

Tom: I can’t make it. I haven’t even started it yet. Can we hand it in next week? 

Maggie: I don’t know. You’ll have to ask Mrs. Robinson about that. I think you must finish it by tomorrow. She probably won’t accept projects after tomorrow. 

Tom: I’ve had so many other things to do. I couldn’t even start it. I don’t know what to do. Maggie: Don’t worry. I’ll help you. It’s not very difficult. I finished it in one day. 

Tom: Really? Great! 

Maggie: First, you should read the article that Mrs. Robinson gave us. It’s about the Mohican Civilization. Then, you have to design a poster for a play about them – the Mohicans – for the theatre.

 Tom: Yeah I know but it looks a bit difficult…  

Maggie: Not at all. You don’t have to make the poster from scratch and it doesn’t have to be a work of art. There are lots of templates on the internet. You can just use one of those designs to make your own poster. 

Tom: Well, I think I can do it. What title shall I use? Can you help me? 

Maggie: Yeah, I can give you some suggestions but you mustn’t use the same title as anyone else in our class. You have to create your own title.

 Tom: Okay, I can come up with something I guess.

 Maggie: Alright? 

Tom: Yeah, I’ve got to go now and make a start on it. I’ll follow the project guidelines like you said. Thanks, Maggie. 

Maggie: No problem. Good luck! 

ACTIVITY PRACTICE

Decide if the statements are true or false according to the text.

 1. Maggie has completed her project. ______ 

2. Tom has submitted his project.______ 

3. Tom must ask Mrs. Robinson if he can hand in the project after the deadline. ______

 4. The poster must look great when it’s finished. _____ 

5. Tom must design the entire poster by himself. ______ 

6. Maggie can’t help Tom with the poster in any way.______