Starscream battles the tyrannical oppression of the evil Autobots. He acts as Megatron's science guy and second-in-command, and constantly peppers his sentences with (genuine) admiration for his great leader.
It's all rather creepy to be honest.
" Of course! You're a genius, Starscream! ”
—A Megatron legitimately praises a Starscream for once
Starscream graduated from the Crystal City College as the most ingenious 'bot on all of Cybertron. Then the war broke out. When Optimus tried to draft the genius, he refused, and, as punishment, the Autobots demolished Crystal City before Starscream's very eyes. Fleeing underground, Starscream joined the Decepticon resistance headed by Megatron. 'Screamer threw himself into his work, hoping that, one day, his scientific acumen could be used for peaceful purposes. He got a chance to pursue ideology, even if by somewhat violent means, when an alternate version of Cliffjumper accidentally crossed over from a universe in which the Autobots were good into Starscream's world. With Cliffjumper's help, Starscream created "Glass Gas" bombs to use on the Ark's launching platform to destroy it. For now, it is assumed that Starscream fought in and survived the battle that followed.