Monday is known to be the day when museum doors remain closed. But there are exceptions. 19 of Zurich's museums also welcome you on Mondays.
City Hall of Zurich (during exhibitions)
Graphische Sammlung ETH Zürich (during exhibitions)
gta exhibitions - ETH Zürich (during exhibitions)
Thomas Mann Archive ETH Zurich
Zentralbibliothek Zürich (during exhibitions)
Zurich Succulent Plant Collection
Some museums are only open during ongoing exhibitions. The best way to find out about opening times is to check online.