Real talk, May is one of my favourite months. It's got all the awesomeness of summer, but without all that annoying humidity; and it's got all the beauty of spring, but without all that annoying rain. In my opinion, May just may be the best month out of all of them.
Of course, since this is Montreal, we know how to do May up right. Not only are there a bunch of awesome things to do during this month, but they're all free. That's right, friends. You're welcome.