I’d kind of wondered about the method he used to get the metal he used to escape from the plastic prison in the first place.
For one thing, human beings have a considerable amount of iron in their bodies in the first place. Our blood’s based on the stuff, you know. I seem to recall reading that the average adult male has enough iron in his body to make six or seven large nails… and why didn’t Magneto notice this before?
In the comics, he routinely screwed people up by using this to “reverse their blood flow,” which was apparently a rather painful and disorienting experience…