Must or have to are used to indicate that a person has an obligation to do something, or that it is necessary for them to do it. Must and have/has to are used in the present and future tense.
Must is used to state someone's personal opinion that something is important to do.
Must is followed by the infinitive without to.
Have/has to is used to give information about an action that is an obligation or a necessity because of rules or laws or because someone obliges you to do it.
Note: often in affirmative sentences we can use must and have to with little difference in meaning because a lot of things are important both because we think so and because they are rules and facts.
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The paparazzi must stop invading people's privacy. |
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The past tense for must and have/has to is had to.
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Must not/Mustn't is used to state that it is very important that something is not done or does not occur because it is against the rules or against the law.
Don't/doesn't/didn't have to is used when something is not necessary for you to do.
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You mustn't smoke in this room because there is flammable material. |
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Have to is used in the question form with do, does, and did.
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How often does the Queen have to talk in public? |
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