The Metaloid was created by the UN in 2457 to help fight terrorist organizations in the southern countries.
It is made up of a multitude of metal alloys including fire-proof steel and titanium.
It is controlled via a radio signal, and can be used from 70 KM away.
The production of the Metaloid was abandoned in 2463 after an incident where terrorists interrupted the signal sent and controlled the machine, killing 12 people.
A train carrying 7 of them was taken over by terrorists and the machines transported to their base where they have been modified to only obey commands sent be the terrorists using a different radio signal than the UN.
(This is obviously a made-up story.)