If the domains line up with each other in a piece of metal you have a magnet; if the domains do not line up the magnetic field cancels and the piece of metal is not a magnet, although the individual a...If the domains line up with each other in a piece of metal you have a magnet; if the domains do not line up the magnetic field cancels and the piece of metal is not a magnet, although the individual atoms still cause each domain to have a magnetic field. One way to destroy the magnetic field of a magnet is to drop it or heat it so that the domains reorient in such a way that the total field is zero.