first/third-person singular present of müssen

necessity, a must

There has to be order.

(idiomatic) A jocular expression used to encourage or justify the consumption of alcohol, especially wine, with fish dishes.

Behave as those around do, so as to not get into trouble; when in Rome, do as the Romans do

in for a penny, in for a pound

one should strike while the iron is hot

(idiomatic) If the mountain won't come to Muhammad, Muhammad must go to the mountain