What types of metals can become magnets when exposed to a magnetic field?

The types of metals that can become magnets when exposed to a magnetic field are iron, nickel, and cobalt. These metals are considered ferromagnetic materials, which means they possess the ability to become magnetized when subjected to an external magnetic field.

In ferromagnetic materials, the magnetic domains—small regions where the magnetic fields of atoms are aligned—can align in the same direction when an external magnetic field is applied. This alignment allows the material to exhibit strong magnetic properties. Even after the external magnetic field is removed, some of these materials can retain their magnetization, leading to the formation of permanent magnets.

In contrast, metals like copper, gold, and silver are not ferromagnetic; they do not have the unique properties that enable them to become magnetized in the same way. Similarly, aluminum and titanium are considered paramagnetic and do not have the same level of magnetism as iron, nickel, and cobalt. Lead and zinc also do not have ferromagnetic properties and thus will not become magnets when exposed to a magnetic field.