Metal is one of the three resource types used to expand and supply your empire.
Metal is the more easily obtained of the two resources that can be mined from asteroids, Crystal being the rarer and more valuable counterpart. Volcanic Planets have only metal asteroids in their orbit, as opposed to Ice Planets that only have crystal. Metal is also the more common element in other planets, Home Planets usually have two metal asteroids and one crystal asteroid. Each race has research that can be done to increase the efficiency of metal extraction. Metal is removed from asteroids by the fairly cheap Metal Extractor.