Nouns ending in -ée are usually feminine, but le musée is masculine.
Musée is one of the rare exceptions: learn it as it is.
Is musée masculine or feminine?
lemuséeexception
The rule behind it
91.7% of -ée nouns are feminine
In context
On construit un nouveau musée dans le centre-ville.
A new museum is being built at the center of the city.
Le musée n'est pas ouvert le lundi.
The museum is not open on Monday.
Le musée est ouvert du lundi au vendredi.
The museum is open from Monday to Friday.