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Meaning of the basic modal verbs and "have to" in a table

Verb	Negative form	Meaning	Examples
can	cannot (can't)	abilities, physical or intellectual a possibility to do something	I can speak German. You can run fast. I can help you. He can call a cab.
must	mustn't	must — need to mustn't — wrong, not acceptable	I must hurry or I'll be late. Son, you mustn't behave like this.
should	shouldn't	recommendation, it is a good thing to I think ... should / I don't think ... should	It's an interesting video. You should watch it. I don't think you should care about it.
may/might	may not/might not	be allowed, have a permission something is probable but not completely sure	You may not speak loudly in a library. Dan might not come tomorrow. He says he might have some other plans.
have to	not have to	have to — obligation, necessity not have to — no need	We didn't have money for the taxi so we had to walk home. It is the same contract as last year. You don't have to read it again.