You mustn't smoke in here

Aim of this lesson: Introduce and practice modals of deduction and use some language related to hotels and other accommodation.

Sally is a tourist and she's visiting Dublin for a few days. She has just arrived at the Victoria Hotel.

Dialogue

	Next Dialogue
Sally	Hello, my name's Sally, and I have a room reserved for tonight.
Receptionist	Hello, Sally. Welcome to the Victoria Hotel. Can I have your passport please?
Sally	Here you are.
Receptionist	OK. It'll be €55.00 for the night. Your room number is 405 and it's on the fourth floor near the lift.
Sally	Great, thanks. Can someone help me with my bags, please?
Receptionist	Certainly. Roger, our porter, will show you to your room.
Roger	Here's your room. Is this OK for you?
Sally	Yes, it looks fine.
Roger	There are some hotel rules which I must tell you about. Firstly, you mustn't smoke in the room and you mustn't make a lot of noise after 10pm. Also you have to vacate the room before 10am.
Herr Schwarz	OK, that's not a problem. Are non-guests allowed in the hotel rooms?
Franz	Yes, but they have to leave before 10pm. Enjoy your stay at the Victoria Hotel. Good evening.

Modals of obligation are used to talk about permission and prohibition.

English for B2 students Grammar • Unit 10 Modal Verbs
Modal verb	Explanation
must	obligations (often personal obligations)
mustn't	prohibited, forbidden
have to	obligations (often external obligations)
don't have to	not required, optional
should	recommended, advised
shouldn't	not recommended, not advised
In most situations must and have to are interchangeable. We often use must when we refer to personal obligations (I must go now because it's late). We often use have to to talk about external obligations which are not our choice (You have to pay taxes). However you are more likely to see must used on signs and in formal situations.
All of the modal verbs remain the same in the 3rd person (i.e. I must, You must, He/She must) except for have to (3rd person is has to).
All of the modal verbs are followed by a verb in the infinitive (I shouldn't smoke)
The past tense of must is had to. The past tense of have to is also had to.
Have to is never contracted. "I have to go to work" NOT ~~"I've to go to work"~~

Work with a partner if possible to answer these questions.

Does your workplace or school have many rules? What mustn't you do?
Can you think of any rules in your local café or shop? What things must or mustn't you do?
In some countries like Australia you have to vote in elections. Do you think this is a good idea?

Try these questions to see if you can use modal verbs correctly. The answers can be found here.

Complete the following sentences using the correct modal verb:

I'm very sorry but you mustn't / don't have to smoke here.
Sir, you have to / must leave your passport at the reception.
My doctor says that I shouldn't / should smoke.
The bus was cancelled so we had to / must take a taxi.
I mustn't / don't have to go to work on Saturday because the office is closed.

For further information about the use of modals of obligation see Modal Verb on Wikipedia.