The substances have been classified as ferromagnetic, paramagnetic and diamagnetic according to

According to electron theory spinning motion of the electrons contributes mainly to the magnetic properties. As diamagnetic substances has paired electrons net magnetic moment due to spin motion is zero. Paramagnetic materials has unpaired electrons so they have a permanent magnetic moment, but they are randomly oriented in the absence of external magnetic field. Ferromagnetic materials have magnetic molecular dipole and due to strong molecular interactions, they form domain. So, electron theory can explain magnetic properties.