Ferromagnetic materials are substances that can be magnetized and retain their magnetic properties even after an external magnetic field is removed. This behavior is due to the alignment of magnetic moments of atoms within the material, which can occur in materials like iron, nickel, and cobalt. These materials exhibit strong magnetic attraction and are commonly used in various applications, such as electromagnets, transformers, and hard drives. The ability to become magnetized makes ferromagnetic materials essential in the development of modern technology and electrical devices.