Montreal is good fun, LOTS of drinking culture if thats your thing, you cant go wrong if you google "Good bars in montreal" but I suggest Philemon, Distillery No. 1, or Bar George.
I suggest going inside the Notre Dame Basilica
The Musee des Beaux-Arts is worth a visit.
Rent a city bike and bike around Old Montreal its so quaint.
If shopping is your thing hit up the Boutiques at the Mile End
If you have the money the Bota Bota spa or Spa Nordique are AAAAAmazing
Eat some poutine, I promise its worth every fatty bite :)
We just came back from a short trip to Montreal last week. Here are the things we did -
(1) Parc Mont-Royal/ George-Etienne Cartier Monument. You can hike/bike or drive up there. You can also take the bus.
(2) Montreal Olympic Park and Observatory - awesome view from the leaning tower.
(3) Parc Jean Drapeau - there was an international food festival going on that time.
(4) Notre-Dame Basilica of Montreal and nearby historic harborfront district
(5) Day trip to Mont Tremblant and the charming village of Sainte-Agathe-des-Monts.
We were traveling with kids and did not eat out/drink at all while there (that's why we love Airbnb's !!). However, we really enjoyed the European character of the city.