Why do magnets stick to refrigerators?

The answer

Magnetism arises from the spin and orbital motion of electrons, which generate tiny magnetic fields. In ferromagnetic materials like iron (found in refrigerator doors), billions of atomic magnetic moments can align in the same direction within regions called domains. When a magnet is brought near, it aligns these domains, creating an attractive force. This is why only certain metals are magnetic - most elements have electrons whose magnetic moments cancel out.