Without reading above, I can distinguish bands actually playing in the movie, and movies with metal songs in the soundtrack, plus movies about rock/metal bands real or imaginary.
In the first case I can remember:
Armored Saint - "Hellraiser III: Hell On Earth"
Cannibal Corpse - "Ace Ventura"
Kiss - "Kiss vrs The Park Phantom" (or some crap like that).
Lemmy - "Airheads" (appearing not playing)
Alice Cooper - "Prince Of Darkness" (appearing not playing)
In the second case (wow, let's see):
"Bad Boys" (1983): Iron Maiden - 'Prodigal Son'
"Airheads" (1994): Motorhead - 'Born to Raise Hell' (can't remember the rest)
"The Frighteners" (1996): '(don't fear) The Reaper (cover not by BOC)
"Interview With The Vampire" (1994): 'Sympathy For The Devil' (cover not Rolling Stones)
'Detroit Rock City' - (1999): AC/DC, KISS, others.
"Prince Of Darkness" (1987): Alice Cooper - 'Prince Of Darkness'
"Wayne's World" (1992) - various (I hate Mike Myers so i didn't see the movie)
"Bill & Ted Bogus Journey" (1991) : score by Steve Vai (according to Steve)
"Twister" (1996): Deep Purple - 'Smoke On The Water' (but the video shown is Rainbow live
)
"Almost Famous" (2000): Black Sabbath - 'Sweet Leaf'
"Last Action Hero" (1993): AC/DC, Queensryche, Tesla, Aerosmith, Megadeth, Def Leppard, others.
"Heavy Metal" (1981): Black Sabbath - 'Mob Rules', Blue Oyster Cult - 'Veteran Of The Psychic Wars', Nazareth - 'Crazy? (a suitable case for treatment)', Cheap Trick - 'Reach Out', Grand Funk Railroad - 'Queen Bee', Sammy Haggar, Journey, others.
For the last case:
"Almost Famous" (2000)
"Still Crazy" (1998)
"Velvet Goldmine" (1998)
"The Decline of Western Civilization Part II: The Metal Years" (1988)
My brain is numb, next please...