You learn everything Ethan knows; how it will pull metal from the ground to prep for evolution and build its new body. You also remember from your time in the Steelix Tails that the Beldum pulled just about any piece of nearby metal that wasn't strapped down; while it pulled that one chick's hairpin through her eye, the Pokeballs on people's belts were perfectly OK. Most of the metal came from a literal stream of metal from the ground, completely obscuring the Beldum before it became a badass.