Why are metals good conductors of electricity?

Metals are good conductors of electricity primarily due to the presence of delocalised electrons that can move freely throughout the metallic structure. In metals, the atoms are arranged in a lattice and the outermost electrons are not tightly bound to any specific atom. Instead, they form a 'sea of electrons' that are free to move in response to an electric field. This movement of charged particles allows for the efficient transfer of electric current.

The ability of these delocalised electrons to flow easily underlies why metals efficiently conduct electricity, making this characteristic a defining feature of metallic bonding. The more freely the electrons can move, the better the metal can conduct electricity. In comparison, other options do not accurately capture the fundamental reason behind electrical conductivity in metals—solid structure alone, fixed electrons, or thermal conductivity do not involve the essential role of delocalised electrons in the conduction process.