Trivia

He played and worked with Suicidal Tendencies, Glenn Tipton, Ozzy Osbourne, Infectious Grooves, and now Metallica.

Replaced Jason Newsted as permanent bassist for Metallica (24 February 2003).

Was a straight A student in school and was often picked on.

Two children with longtime girlfriend Chloe: Ty Orion and Lula.

In the documentary Some Kind of Monster (which was supposed to be a reality show), the three members of Metallica were impressed that Robert could not only keep up, but he could play both with a pic and his fingers to the band's fastest songs.

As a child actor, on an episode of CHiPs Robert played a young Hispanic boy who Erik Estrada's Ponch helps. Before that he played a little boy in the medical comedy House Calls starring Walter Matthau.

Lives in Topanga, California.

He was also the bass player on Jerry Cantrell's album "Degradation Trip.".

He originally intended to be an orchestra conductor.

Is the youngest member of Metallica.

He is of Mexican descent.

Has also filled in as the bassist for Zakk Wylde's Black Label Society on Ozzfest 2002 on the main stage, handling both bass duties for Black Label Society's set and Ozzy Osbourne's headlining set, and also for Black Label Society's 2 week headlining mini tour after Ozzfest 2002. One of the stops on the 2 week mini tour was filmed in Detroit for a Black Label Society DVD, which he also appears on as well.

While the funky slap-bass style that he played in his previous bands doesn't suit Metallica, he does slap the bass (and rather hard at that) during bass solos live with Metallica.

Along with bass he can also play the guitar. On one video, he impresses James Hetfield by playing the Flamenco Guitar, which is one of the hardest styles to play.

Despite being the longest-running bassist with Metallica, he's played on less Metallica studio albums than both Jason Newsted and even the original bassist Cliff Burton, who, before his death in 1986, played on their first three albums. As of 2021, Robert has only played on two studio albums. It will take two more albums to surpass Burton, who was only in the band for only five years (albeit extremely important years) compared to Robert's almost twenty-years with the band.

Replaces Jason Newsted as permanent bassist for Metallica <> (February 24, 2003)

Despite being a member since 2003, the only studio albums he has played on with Metallica so far are "Death Magnetic" (2008) and "Hardwired...To Self-Destruct" (2016). The 2011 double album "Lulu" doesn't count, as it's collaboration record between Lou Reed and Metallica rather than a traditional Metallica album.