The red lands of the plane of Mirrodin are mountains of metal, mostly rusted iron. Scrap metal piled high, combined with structures of pipe and plate, form peaks where Mirrodin's goblins -- and many other heat-happy creatures -- live.
Below: A sketch of a rusty mountain range by Mark Tedin. These mountains definitely have the Mirrodin "metal world" look, replacing dry rocky peaks with hammered metal and twisting ductwork.
Below: A full-color concept illustration by Mark Tedin. See the metal "boulder" floating above one of the peaks? Mirrodin's mountain ranges generate strong magnetic fields which cause these anti-gravity anomalies (see also any of Mirrodin's basic mountain2s). The mountains are also home to the human Vulshok, hardy artificers and warriors (see Vulshok Battlemaster or Vulshok Berserker, or their Vulshok Battlegear).