Essentially, magnetic force is electromagnetic force, which is one of the four fundamental natural forces. The generation of magnetic force needs to be explained at the atomic scale.

For an atom, its center is a nucleus composed of protons and neutrons (hydrogen nuclei only have protons), and the periphery is an electron moving around the nucleus. But unlike planets that orbit stars in precise orbits, the positions where electrons appear are random, and only the probability of electrons appearing at a certain position can be known.

According to quantum mechanics, the spin of electrons and their motion in orbit both generate a dipole magnetic moment, which forms a magnetic field. Similarly, spinning atomic nuclei also form a magnetic field, but this is much weaker than the magnetic field generated by electron magnetic moments. The various magnetic moments in an atom will be superimposed and cancelled, resulting in a total magnetic moment - the atomic magnetic moment.

Under the action of a magnet or magnetic field, the atomic magnetic moment arrangement of metals such as iron, nickel, and gadolinium becomes highly ordered, which superimposes on each other to produce a net magnetic moment, forming a magnetic field, and these metals will be magnetized. Therefore, there is a strong electromagnetic force between metals such as iron, nickel, and gadolinium and magnets, which is called magnetism, causing metals such as iron, nickel, and gadolinium to be attracted by magnets. And the atomic magnetic moments of other metals such as copper and aluminum do not become highly ordered under the action of magnets, so they cannot generate a strong enough magnetic field to be attracted by magnets.