Anvil is probably the best choice for Ontario, and since I'm one of the few that still likes them, I'll make a case for them.
In terms of influence, Anvil are probably among the more important metal bands (certainly not a top 10 band or anything, but probably top 100). Their second and third albums were landmarks in speed metal, not necessarily for the speeds themselves, but more the attitude, image, and the way it all came together.
From a longevity perspective, few bands can rival them. Much like Motorhead, they continue to put out album after album of consistent, solid heavy metal. I think Motorhead is a great comparison because there isn't really any point in their career that you could say was different or awful, but there are definitely low points and high points. Despite that, every Anvil fan probably has a different favourite record if you exclude the first three, so no part of their career can really be disowned.
Surprisingly, Anvil is one of the more popular metal bands from Toronto (or Ontario). Many of the other great choices from the 80's never reached their levels of popularity (Razor, Infernal Majesty, Sacrifice, etc.), and many of the current bands are just too young and unestablished to really qualify for a "Hall of Fame" (Skull Fist, Cauldron, etc.). Even if everyone has forgot about them since the documentary, Anvil did become quite popular at that time, and they were definitely headliner material in 1983.
4/24 - Skull Fist
5/3 - Dragonforce
5/16 - Cauldron
5/23 - Axxion, Night Demon
5/28 - Sepultura, Destruction
6/20 - Bolt Thrower