Iron is a metallic element that possesses strong supernatural properties, and is thus used by hunters when combating certain supernatural creatures. Iron is especially painful and deadly to demons as well. Touching iron will burn a demon, they also cannot cross iron, much like salt. Their weakness to iron is so strong, that even Azazel, one of most powerful demons, who was immune to many other demon weaknesses, was still affected by iron. However, some demons proved to be immune to iron such as Astaroth and Satan himself. Iron is also quite effective against ghosts. While it will not destroy them it will temporarily repel them.