Kill 'em all is my favorite.
When they started creating the albun, they had Carry King from Slayer and Dave Mustain from Megadeth in the line up !!!! I have a live album with them!

did you know the 2 track "the four hoursemen" is different from what wrote?
Dave from Megadeth was with them at that time and the song title was "Mechanix" and they broke up before the album was released, Dave left Metallica to found Megadeth and Metallica changed the song name and even the lyrics, but the music line is the same with the same riffs. You should listen to the Megadeth 1st albun that contains the original soung.

It's a very strong riff album. Master of Puppets it's also great.