Must - English Grammar Today - a reference to written and spoken English grammar and usage - Cambridge Dictionary Please provide me with some clarification on this. Modal verbs are a special category of helping verbs that we use to express possibility, capability, intention, obligation, permission, and futurity. The ice cream here is delicious. A strong recommendation. The second is for the present moment. In American English, have to is more common. (present tense) Each of the drivers had to file an accident report. The first is an appropriate response to someone who has just finished telling you a story about something in the past that exhausted them. That must have been interesting. "must have": we believe the action definitely happened. Something that is highly recommended (stronger than using should) We really must get together for dinner sometime. Must and have to can both be used to talk about necessity. Here are sample sentences: The mail must be lost in the mail. You must see the new Peter Jackson movie, it's fantastic. British English often makes a distinction between them. The mail must have been lost in the mail. She must have been at home - her car was there. Hi, I'm completely confused as to how to use must and must have been. We use "must have", "can't have" and "might have" in the same way as the present perfect - the action we are describing happened, or did not happen, in the past and is still true in the present. MUST – NECESSITY; Must expresses an opinion about what needs to be done in the present or future, and is based on one's personal sense of what is right and what is wrong. The categories of legal person (which includes natural persons) which don’t have legal capacity are: bankrupts; minors (subject to the Minors' Contracts Act 1987) individuals operating under a mental disability (at common law) companies which have not yet been formed, and We must/have to build up a strong army to defend the country. Obligation. Both must and have to can be used to talk about obligation. Are both of these grammatically correct and they both apply to something that is thought to be lost in the mail? To expand on his answer a bit, “must” is one of English’s modal verbs. Mark Kappe is correct. Both are depending on how they're used. Drivers must not make unsafe lane changes. To form a contract, a party must have the legal capacity to do so. VS. Necessity. The passengers in the car must have been extremely frightened. In American English have to is the normal form. "She must have left the house by now; it’s nearly 11 o'clock." Must Summary Chart Mustn't. You must try some. 5.