John Paul Jones was a session player and arranged some songs for the Yardbirds. When he heard Jimmy Page was forming a new group he wanted to be a part of it. His many talents were the backbone of Led Zeppelin and their powerful rhythm section. You have to appreciate the way he walks the bass in The Lemmon Song or his organ playing on Trampled Underfoot.
To save any confusion he is the only member of Led Zeppelin who used a stage name.