Conversation so far:
when did Michael Anthony (musician) get into music?
He took an interest in guitar as a teenager, but picked up the bass instead since most of his other friends already played guitar or drums.
what was his first release?
During this time, bass player Mark Stone parted ways with Mammoth and the Van Halens decided to audition Anthony as a replacement.
Did they like him?
After the session, the Van Halen brothers asked Anthony to join their band.
where did he learn how to be a bass player?
CANNOTANSWER.
what other bands did he play with before Van Halen?
His first band was called Poverty's Children.
Other bands he played in included Black Opal, Balls, and Snake.
did he have hits early in his career?
Snake played covers of ZZ Top, Lynyrd Skynyrd, and Foghat, along with some original songs.
did he go on tour at all during this time?
CANNOTANSWER.

Question: why did he decide to leave the band he was with and join Van Halens?
Self-contained rewrite: why did Michael Anthony decide to leave the band he was with and join Van Halens?