Over the years, Metallica has gone through a few different bassists. Starting in 1982, Ron McGovney was the bassist.
Ron was a childhood friend of Jame's. Along with Dave Mustaine and Lars Ulrich, Metallica was born. However, Ron's time in the band was short lived. After recording the bootlegged demos Power Metal and No Life Til Leather, he was replaced by the bass god, Cliff Burton.
Many claim that Cliff was one of the greatest bassists ever to play. Using a unique style, he played the bass guitar like a regular electric guitar. Cliff can be heard on the first three Metallica albums, Kill'em All, Ride the Lightning, and Master of Puppets. Though one of the greatest bassists of all time, his life was taken from him at an early age. The many dangers of touring claimed the life of Cliff on the Master of Puppets tour. As the tour bus was traveling between shows, there was some black ice on the road. The bus spead out of control and started to roll over on it's side. This continued all the way down the hill. During the process, Cliff was thrown out of one of the windows and the bus landed on him. At the time, they were not sure if that killed him or not. However, when they took the bus off of him, the chains slipped and the bus fell back ontop of Cliff. If Cliff was still alive, that final blow killed him.
With Cliff gone, Metallica quickly needed to replace him for a tour in Japan. There were open auditions and many different bassists tried out for the gig. Competition was tough, even Les Claypool was turned down. Eventually, the band came across a young kid named Jason Newsted. Jason wasn't the greatest player out of the bunch, yet he had the energy needed to be part of Metallica. From that point on, he was a steady member of the band. Jason can be heard on the albums Garage Days Revisited until S&M. After recording the song I Dissappear, for the Mission Impossible 2 soundtrack, he left the band for personal reasons.
Currently, Metallica does not have a bassist. The leaving of Jason was quite shocking, but the three original members have decided to continue without him. They are still working on their new album, the bass part is being played by Kirk, James and their producer, Bob Rock. Eventually, they will get a new bassist. Until then, we can only hope their new cd will have the same edge that their other ten had.