3Main values / meaningsMust – obligation imposed by the speakerHave to – obligation imposed by a situation (external obligation)
4MUST & HAVE TO I must finish my homework before 8 We have to start work at 9 amThey are both used to express that something is necessary
5MUSTI must find a hotel to stay at tonight (“I have to find a hotel” is also possible)The speaker decides that something is necessary (INTERNAL decision)
6HAVE TO I have to wear a uniform Somebody else has made the decision, it’s not the speaker’s opinion (EXTERNAL decision)
7MUSTN’T & DON’T HAVE TO Very different meanings in negative: You mustn’t open the doorYou don’t have to open the door
8Affirmative / negative differences Have to (obligation) /vs/ don’t have to (lack of obligation)Must (obligation) /vs/ mustn’t (prohibition)
9MUSTN’T & DON’T HAVE TO Very different meanings in negative: You mustn’t open the doorYou don’t have to open the door
10MUSTN’TYou mustn’t open the door. Lately there have been many robberies in the neighbourhood.(It’s forbidden /prohibited)
11DON’T HAVE TO You don’t have to open the door. I have the keys. (It’s not necessary)
12Student worksheet 1Modals and Related Expressions must have to 1. I ……….be at the meeting by 10:00. I will probably ………..take a taxi if I want to be on time. 2. You ………..submit the application if it has not been completely filled out. Check that the name, address, and background information are correct. 3. A: Look at these flowers - they're beautiful! But, there's no card. Who could have sent them? B: It ………have been David. He's the only one who would send you flowers.
134. You ………. forget to pay the rent tomorrow 4. You ……….forget to pay the rent tomorrow. The landlord is very strict about paying on time.5. You ………….. be so rude! Why don't you try saying "please" once in a while.6. If you are over 18 in California, you ……. take a driver training course to get a driver's license.7. You …………be rich to be a success. Some of the most successful people I know haven't got a penny to their name.