>>16889481The plates are always within Arceus (in that giant circular belly in the center of its body), and they've only been shown externally when Arceus calls them out itself or when it uses them to stop an extremely significant force (the meteor that was going to strike the planet).
In a battle they would never be seen, and it would effortlessly change its Type to resist any attack thrown at it. In the film the only reason anything can harm it is because it lent some of the Plates to the humans to rebuild their land, making it vulnerable to the Types it gave up. With all of them, it's likely invincible in battle.
It's also capable of freezing everything around it and fixing it back to what it used to be, moving everything with free will (which is what it did when it was restored with its missing plates), though I'm not sure if that was time stopping or just it levitating everything.
tl;dr - Movie Arceus is probably the most broken thing ever.
