Tommy Lee went LIVE WIRE Sunday night in Vegas -- all over Nic Cage's son Weston -- with bloodbath potential.
Nic and Weston were at the Mötley Crüe show at the Hard Rock Sunday night ... hanging out backstage with Vince Neil after the show. We're told when Tommy tried entering his dressing room ... Weston blocked his path -- it appears it was unintentional.
Tommy tried to shove past Weston ... telling him to get the f**k out of his way. Our sources say Weston then went nuclear, screaming and swearing at Tommy and challenging him to a fight.
Tommy then came unhinged ... getting in Weston's face and screaming at ear-piercing levels.
Just before certain violence was about to erupt, Mötley Crüe's security moved in and removed Weston and Nic from the immediate area.