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 produce magnetism. However, in most substances, the directions of the electrons' movements are different and chaotic, causing the magnetic effects to cancel each other out. Therefore, most substances do not exhibit magnetism under normal circumstances.

Iron, cobalt, nickel, or ferrite and other ferromagnetic substances differ; their internal electrons 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 aligned and oriented, which strengthens the magnetism, 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's opposite poles generate an attractive force, causing the iron block to firmly adhere to the magnet. We say that the magnet has magnetism.