" @MisterShin: True, but Does that mean it's not made of metal? "
This is true as well, in Naruto their has never been stated to be items that are made of unknown materials.
Everything is either made of normal earthly materials or infused with chakra (Kakashi's fathers white fang sword, was infused with chakra that gave a white trail or something).
Legendary Items that itachi has in his Susanoo is some sort of Chakra item i believe, considering Susanoo is a great mass of chakra.
However Misaka wins Iron Sand to shield (similar to Gaara), Lightning/Railgun to attack. @hitsusatsu11
Going back to what you said about Zanpakto's they are extentions of a Shinigami's spirit, thereby not actually containing any trace of metalic properties so it cannot be controlled via magnetisim.