The auxiliaries must and have (got) to express a need or
	an obligation.

A - Construction of must

•			The auxiliary must is conjugated in the same way for
		all persons: it does not take an -s in the 3rd person
		singular.

•			Must is followed by the infinitive without to.

•			Must is only used in the present simple.

		Example:	You must wash your hands before eating.
							
	Note: With must the questions and negations are formed without "do".
	Example:	Must we bring sleeping bags? - You mustn't open the door
	to anyone.