Think back to 2008, when Marvel Studios released their first feature film, Iron Man. Despite the two being completely unrelated Marvel brought Black Sabbath's Iron Man into the fold, adding it to the end credits and using it in marketing. Now someone's gone and added it to the climax of Avengers: Endgame's final battle, and the results are damn-near perfect.
Reddit user u/bobleecooper added the Black Sabbath track to the climax of the big battle with Thanos, you know the point where Tony sneakily steals the Infinity Stones and snaps the bad guy army into oblivion. See for yourself below, but even if you're not a Sabbath fan you have to admit the timing is just perfect. I'd say it's even better than Thor: Ragnarok's bridge scene that replaces Led Zeppelin for Abba.
The track begins as soon as Thanos snaps his fingers to try and annihilate the universe, which is a stroke of genius in itself, but then the track is perfectly synced to the rest of the film. The lead guitar fires up the main riff right as Tony snaps his fingers. It's almost as though it was deliberately set up that way, though like The Wizard of Oz and Dark Side of the Moon it's probably just a coincidence.
Not to knock Alan Silvestri's score or anything, but I'd much rather see a version of Endgame where the song continues. We see a little bit of Thanos's army being dusted into nothingness while the song plays, but dammit I wish I could see more. Sadly my AV skills aren't nearly good enough to sort that out for myself. This will certainly do for now, though it's a shame the original didn't feature this song at all.
Endgame was basically a three-hour tribute to Tony Stark (among other things), and it's a bit of a shame we never got some of the same musical callbacks to the original film that Captain America got. So if anyone from Marvel is listening we need more Black Sabbath and more
Led Zeppelin AC/DC.