Must and Have to, can be used to express obligations. Simply put: Must expresses a personal obligation while Have to an impersonal obligation or a fact. As Christmas is not far off my mother has given me the following obligations:
Well, my plan is to avoid going back to the UK for Christmas so I don’t have to do any of the above. Furthermore, I would rather slit my own wrists and cut out my tongue than drink eggnog. Eggnog is for nutjobs and dairy lovers!
Seriously, what’s the problem with looking like a scarecrow, talking about my new favourite Spanish sitcom, ‘Gym Tony’, and drinking vodka?
In general the difference between Must and Have to is connected to personal opinion. If it is your personal opinion to do something then usually we use MUST + BARE INFINITIVE, and if it isn’t connected to your opinion, for example an external situation, then we usually use HAVE TO + BARE INFINITIVE.
My hair looks like a bird’s nest I must go to the hairdressers.
I must phone my mother because I’ve not spoken to her for a month.
My nephew has to go to school
I had to walk home last night as I missed the last bus.
We use Must or Have to, to say that it is necessary to do something. Often it doesn’t grammatically matter which you use. However, in some situations they mean different things. Must is used when we are giving our personal feelings and Have To is used for impersonal things, for example a rule or a situation. Examples:
I must get up early tomorrow. (There are a lot of things I want to do) PERSONAL
I have to get up early tomorrow. (I’m going on holiday and my flight leaves very early) IMPERSONAL SITUATION
I must wear a suit. I want to look good. PERSONAL
I have to wear a suit. It’s the company’s policy. IMPERSONAL RULE
You mustn’t park here. It is against the law.
You don’t have to park here. You can if you want to, but you could park somewhere else.