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Why can metals conduct electricity?

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Diagram showing four types of crystal bonding: ionic bonding with sodium and chlorine ions, covalent bonding with carbon atoms sharing electrons, metallic bonding with iron ions surrounded by free electrons, and molecular bonding with hydrogen molecules held by weak electrical attraction. — chemical bonding Different types of bonding in crystals.

Metals are able to conduct electricity primarily due to the presence of non-localized valence electrons, often described as a "sea" of free electrons.12

In a metallic structure, the outermost electron shells of neighboring atoms overlap, allowing valence electrons to detach from specific atoms and move freely throughout the entire crystal lattice. These electrons are not bound to any single pair of atoms, which distinguishes metallic bonding from covalent bonding.1

When an electrical field is applied to the metal, these mobile valence electrons are free to move, creating an electric current. While the number of these conduction electrons is important, a metal's overall conductivity is also determined by the mobility of the electrons—the ease with which they can travel through the solid. Factors such as crystal defects, impurities, and temperature-induced vibrations can cause electrons to scatter, which increases electrical resistance and hinders their movement.132