Magneto's plan is to use Rogue in his machine, which requires grabbing two handles by the hands.
She is handcuffed to the machine (both made of metal) and we see that Magneto puts his hands on her face, and she starts to receive his powers, and then she seems to be forced to grab the handles of the machine.
Of course, Magneto can move the handcuffs to get her hands close to the handles but since Rogue is not made of metal how is she forced to grab the handles of the machine?
When Magneto first operated the machine, he was nearly killed by it because of the strain it put on his body. Because of this, Magneto needed a 3rd party, a vessel, to operate it. Magneto chose Rogue because she was young and easily manipulated, but also because her power is the ability (whether wanted or not) to absorb the powers of others. If Magneto was to transfer his powers to someone to run his machine, who better to pick than someone with the predisposition to absorb powers? Wolverine, with the ability to regenerate, would have also been a good pick in theory, but Wolverine wasn't one to be easily controlled. So Rogue was chosen.
When Magneto transferred his powers to Rogue, she became prone to attracting metal, hence the handles became attracted to her.
Rogue has serious problems controlling any power she absorbs. It pretty much always goes awry.
In this case, she made her own hands attract the handles because she was not able to not activate Magneto's absorbed power.
