NOTE: This'll probably only make sense if you read my Cyberverse Galvatron's Bio first.
“We are honoured to make you a part of our team Galvatron, remember as you wear this badge you are a member of our family. We are all here for each other and you, we shall never abandon you… remember, you’re safe from Megatron now, we will protect you” Optimus Prime beamed at the newest addition to their group, clasping his servos to his shoulder struts, “I mean it.”
So yeah, after Megatron's brutal experiments on him and the heartbreak of Cyclonus's sacrifice (they do not know his fate yet) and being in a place where he only knew barely a handful of bot's Galvatron was naturally pretty depressed and withdrawn. So, Optimus whose dang-near adopted Galvatron (in his mind) at this point decides to make a point of holding a mini-initiation ceremony for him.
Galvatron is very shocked and probably tries to pretend he's not crying from happiness. That shade of red just irritates his optics HONEST.