Disney Vs Non-Disney Villains War
His first appearance occured after Megatron was defeated by Gantu. Soundwave carried Megatron off to Mok Swagger who used his supercomputer to upgrade Megatron into Galvatron. Afterwards, Galvatron was not scene fighting. It is possible that he fought other villains or even heroes for Mok behind the scenes of the main fight but nothing has been confirmed.
Disney Vs Non-Disney Villains War - Part Two
Galvatron's second appearance was in a flashback during the Second War. After Mok's defeat, Galvatron hid
inside the remains of his fortress, controled by Mok's supercomputer but with the desire to break free and enact his revenge on Gantu. It wasn't until the Quarrymen arrived that Galvatron had his chance. At first he started to attack them, but then they revealed they were going to destroy Mok's computer. He let them destroy it. He automatically refomatted back into Megatron, but this time with a more powerful body.