Jason Newsted would only re-join Metallica for a "squillion dollars".
The bass player was added to the 'Enter Sandman' group in 1986 to replace Cliff Burton - who had died in a road accident - and had a turbulent relationship with some of the members until he left in 2001.
While he says he would theoretically rejoin them onstage if anything happened to current bass player Robert Trujillo, it would only be if certain conditions were met.
He told Swedish blog Metal Shrine: "If they were 'brofessional' about it and if they came as my brothers and they were professional with the meeting and they're sitting there and looking me in the eye and the managers aren't around.
"If it was like that again and the money was crazy, then I would consider it. But it would be only for that thing and it would be absolutely delegated. It would have to be these 30 shows in these 45 days for this squillion dollars. But it has to be that."
Jason, 49, now plays in his own project, Newsted, and says his relationship with the other members of Metallica - Kirk Hammett, James Hetfield and Lars Ulrich - has improved.
He added: "I love those guys and I always will and I will defend them to the end of time.
"I'll always have respect for those guys, because they gave me my chance. They gave me my chance and I'll never ever forget that. Now, we've had our differences over time but that s**t is under the bridge a long time ago."