Metallica's bass player. He's from Battle Creek, Michigan. He was born March 4, 1963. He was in Flotsam and Jetsam and Dogz before Metallica.

Its important to note that Jason has, in fact, left Metallica, as of January 17, 2001. I didnt know Jason had left the band until this morning, 23 May, 2001! I was shocked and could not believe it. Anyway, Metallica are back in the studio, so I am assuming they have found someone else to play the thick strings.