Why do metals conduct heat better than many other materials?

Metals conduct heat more effectively than many other materials primarily due to the presence of a high density of free, delocalized electrons. In metals, valence electrons are not bound to individual atoms but are free to move throughout the entire crystal structure. These mobile electrons act as efficient carriers of thermal energy, rapidly transporting heat through the material.12

In contrast, non-metallic materials typically have electrons that are more tightly bound in valence or ionic bonds, making them less effective at transferring energy. While heat can also be carried through solids by phonons—units of vibrational energy arising from oscillating atoms—the additional, highly mobile electron population in metals provides a superior mechanism for thermal conduction. This relationship between electrical and thermal conductivity in metals is described by the Wiedemann-Franz law, which notes that the ratio of thermal to electrical conductivity is nearly the same for most metals at a given temperature.3425