Must mean "required" Used to force an action according to the rules as necessary, unavoidable. If it is to avoid going would be punished or have adverse consequences, with the following format.
must mean "need" to use. Forced to take action according to the rules. It is imperative inevitable. If the inevitable happens, it will be punished. Or have adverse consequences The following figure
Must means "to" used to force the action according to the rules. It is necessary to avoid. If there is to avoid the happen, it will have to be punished, or bad, followed by a form as follows.