Iron style: using Iron from your blood to produce fighting polls,blades and other weapons infused with chakra nature
Crystal was already used in the three tails arc and metal is essentially the same as the iron sand/magnet release.Earth + Lightning = Crystal
Earth + Fire = Metal (better than lava)
I didn't think of it before the series but i did expand on it with the diamond release.Except that I thought of crystal years before it was used in filler, and planned on the composite elements based on a natural phenomena; when lightning strikes the ground, the dirt is crystallized. In the anime, it was never elaborated upon.
Magnet release is not making metal, it's controlling metal. My metal release is making metal, and molten metal (which looks like lava and would basically function the same, except cool into metal) is also an option of attack.
In fact, a Magnet release user paired with a Metal release user would make quite the team. Perhaps add in a Lightning release user to electrify the metal and perhaps give the Magnet release user a boost would make a great ninja team.