Metallica - Kill Em All

While not as timeless as Ride the Lightning or Master Puppets, Metallica's debut album--originally released in 1983--is still a fine piece of thrash metal, and as good a marker as any for the debut of the genre. Fusing the rapid-fire attack of bands like Motorhead with a guitar style reminiscent of such British heavy metal bands as Iron Maiden and Judas Priest, Metallica essentially created a new kind of metal. Several of the songs from this 1983 album have since become classics, including "Seek & Destroy", "The Four Horsemen", and "Jump in the Fire". The songwriting isn't as sophisticated as on Metallica's later releases; still, it's a great listen, and essential for any heavy metal fan.