Two of the most influential bands in heavy music (and personal favorites of mine) will see documentaries on them released in the (hopefully) not so distant future:
Bad Brains are easily the best hardcore band ever to exist and you would be hard pressed to find any musician who plays that style of music who disagrees (and if they did, then there band probably sucks). Obviously, the band stuck out in a scene dominated by white boys because they were Rastafarians, but they also stuck out because they were faster, louder, crazier and better than everybody else. The incorporation of reggae into their music made them stand out (and above) the pack and has never been bested by any band since (at least not to my knowledge). The band hasn't sold millions, but they have been hugely influential in the hardcore, punk and metal scenes. One of those bands that launched a thousand bands if you will.
Here is a teaser for the documentary:
"Big Take Over"
"I Against I"
And speaking of bands who launched a thousand bands, Motorhead is getting the documentary treatment as well. Well, technically the documentary is about lead singer/bassist/all around bad motherf'er Lemmy Kilmeister, but he IS Motorhead (and that's not taking anything away from the superbly talented line-ups he has had over the years). Lemmy: The Movie tells the story of Lemmy's 40+ plus year (!) career. Pretty amazing that the guy is in his early 60's, yet still gigs like crazy all over the world (and has never "retired" only to come out of retirement for a cash-in tour). The guy really makes all other rock bands his age look downright geriatric (well, maybe not Neil Young).
Check out the teaser:
"Ace Of Spades"