Built over three galleries and their underground connections, the museum is moderately sized for a city of 4 million people. It's got collections covering the antiquities to contemporary art and sculpture, but the focus is Canadian art (as it should be) and contemporary Canadian art at that. It's got a lot of RIopelle, Paul-Emile Borduas, Ozias Leduc as well as an impressive permanent exhibit on the Old Masters. It does feature temporary traveling exhibits (sometimes for an extra fee).
The museum is free but donations are encouraged, and you can easily spend an entire afternoon in the museum (3-4 hours). It's best to pick up a map of the museum at the entrance so as to direct your self-guided tour. There are wheelchairs and coat check available if you need them. There is also a museum restaurant in the Demarais Pavillion (the newest gallery) if you want to eat. It's no Met, but I loved it, and I would put it on my "Must See" list for any art lover visiting the city.