To heap praise upon one of the first and best metal songs ever would be hugely redundant, but it'd be impossible to make a list like this without "War Pigs."
The Dillinger Escape Plan, "Pig Latin"
The best live avant-metal band ever teams up with the best avant-metal singer ever for a far-too-short EP, highlighted by Mr. Bungle-echoing math-metal like this song.
Jane's Addiction, "Pigs in Zen"
Jane's Addiction closed out their first masterpiece album with some of Perry Farrell's wackiest vocal stylings ever on record, a perfect Dave Navarro performance and a much better "Zen" pun than Robert Plant's.
Nine Inch Nails, "March of the Pigs"
"Closer" had all the controversy and "Hurt" had the universality, but "March of the Pigs" is probably the strongest single off The Downward Spiral. 7/8 has never been more effective, and the lounge piano segment in the chorus somehow manages to be even more surprising the second time it plays.
Suicidal Tendencies, "Fascist Pig"
Years away from becoming a funk-metal powerhourse, Suicidal Tendencies started by writing catchier and funnier hardcore than any band outside of the DC area. Hear them rage harder than countless punk albums, band names and t-shirts targeting the Reagan Administration, in a little over a minute.
Anything by Pig Destroyer ("Loathsome," for example)
One of Virginia's finest has probably destroyed more eardrums than they have pigs, but who's keeping score?