Horseshoe magnet. Metal filings being temporarily magnetised by a permanent iron magnet (horseshoe- shaped). Magnetism is mostly a property of metals. It is a force exerted at a distance by a field, in this case generated by moving electric charge on a subatomic level (electrons). The force can attract or repel, with a horseshoe magnet having a north (N) and a south (S) pole with one attracting and the other repelling. The filings will lose their magnetism when they are removed from the presence of the permanent magnet.