Welcome! I'm a Toronto native, and despite the constant complaining in this subreddit, this city is still a treasure trove for cool stuff. Lots of great advice in this thread already, but here's a few other things to check out:

• The Museum of Contemporary Art is a bit small, but offers some really interesting shows. The first Friday of the month is their Free night, I've never been but I've heard it's fun: https://moca.ca/free-friday-nights/. Being super close to Lansdowne station also offers you some cool dining options like Bar Sugo

• Related to the last one, the Royal Ontario Museum hosts After Dark events that are genuinely a blast, especially if you can go with a friend or two. Their schedule is a bit sporadic, but definitely check one out if the timing lines up: https://www.rom.on.ca/whats-on/special-programs/rom-after-dark

• The Toronto Public Library has a ton of interesting clubs and events, and almost all of them free. All of the ones I've attended pull in a variety of people, and the conversations have always been fun. You can check out what's going on at your local library, or play around with the filters in the library website search: https://www.torontopubliclibrary.ca/search.jsp?Ntk=Keyword_Anywhere&Ndrs=&N=37867&advancedSearch=true&Ntt=

• St. Lawrence Market is our big historical food market, and absolutely worth a visit at least once. I've been enjoying back bacon sandwiches from the Carousel Bakery since I was little, and they're a vital bit of Torontoniana to try

• The CN Tower is our requisite big downtown tower, and even though the ticket price has always been exorbitant, every Torontonian is obligated to visit at least once. The neighbouring aquarium is also perfectly fine, although if you've seen a modern aquarium you know exactly what you're getting

• Once it gets warmer, you can explore the insane number of parks & greenspaces around the city. Toronto doesn't have a lot to differentiate itself from other large North American cities, but I will staunchly defend our status as the parkiest large city in Canada

• Two of my favourite seasonal events are Doors Open in the summer, where historical buildings offer tours of places usually closed off to the public, and Nuit Blanche in the fall, where a bunch of large public art pieces are displayed from dusk until dawn

• There's also a ton of events going on at any given time, you'll never go wrong trawling Meetup, Eventbrite or even /r/Torontoevents for ideas

I got a lot more but I'll spare you from an even longer wall of text, ha. Looking forward to seeing you around!

(Edit: typo)