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Why do metals conduct heat and electricity well?

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Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy. — phase States of matter.

Metals are excellent conductors of heat and electricity primarily due to the nature of their metallic bond. In a metallic solid, atoms are closely packed, and their outermost valence electrons are not bound to any specific atom. Instead, these electrons become non-localized, forming a "sea" of free electrons that can wander throughout the entire crystal structure.12

When an electric field is applied, these mobile valence electrons move easily through the material, facilitating the flow of electric current. Similarly, this high mobility allows the electrons to efficiently transport thermal energy throughout the metal.314

The effectiveness of this conduction depends on both the number of free electrons and their mobility—the ease with which they move without scattering off impurities, crystal defects, or vibrating ions. Because thermal vibrations increase with temperature, the scattering of electrons also increases, which is why the electrical conductivity of most metals is highest at lower temperatures.243