"Holy Wars… The Punishment Due" is a progressive thrash metal song which is opening track of Megadeth's fourth album Rust in Peace.
The song has an unusual structure, shifting at 2:26 after an acoustic bridge by Marty Friedman to a different, slower and heavier section called "The Punishment Due", and returns towards the end back to "Holy Wars", after a solo played by Dave Mustaine. The entire song is generally referred to as simply "Holy Wars".
"Holy Wars" is about the Israeli-Palestinian conflict back in 80s, while "The Punishment Due" is based on the popular Marvel comic book character, The Punisher.
"Holy Wars" music video: https://www.youtube.com/watch?v=9d4ui9q7eDM
The song is the last song played during the encore of all recent Megadeth shows and is a fan favorite.
The song is the 3rd most popular Megadeth song in Last.fm, but because of so much miss-tagging the song can only be seen in charts on 13th place mostly.