Most substances are composed of molecules, which are made up of atoms, and atoms consist of atomic nuclei and electrons. Inside an atom, electrons spin and orbit around the atomic nucleus. Both of these movements generate magnetism. However, in most substances, the directions of electron movement are varied and chaotic, causing the magnetic effects to cancel each other out. Therefore, most substances do not exhibit magnetism under normal conditions.

Iron, cobalt, nickel, or ferrites, among other ferromagnetic materials, differ in that their internal electron spins can spontaneously align within a small range, forming a spontaneously magnetized region known as a magnetic domain.

After magnetization, ferromagnetic materials have their magnetic domains neatly arranged and aligned, which strengthens the magnetism, thus forming a magnet. The process of a magnet attracting iron is the process of magnetizing the iron block. The magnetized iron block and the magnet, with opposite poles, generate an attractive force, causing the iron block to firmly "stick" to the magnet. We say that the magnet has magnetism.