Magneto can control non-magnetic metal too.

In the comics, Magneto rips out his skeleton at one point. After which Xavier telepathically lobotomizes Magneto. And yes, although Logan nearly dies, he grows a new skeleton including bone claws. His healing factor also goes into overdrive since it doesn't have to fight against the toxic adamantium all the time. It makes him grow more feral too, until writers decided it got too stupid with Logan talking and acting like a caveman so he got the adamantium back.

I think he grows around his skeleton.

I'm pretty sure that wolverine is technically not immortal (depending on canon) however the Adamantine casing which is pretty indestructible means there's always a piece of him to regenerate from.