Why are metals good conductors of electricity?

Metals are good conductors of electricity because they have free electrons that can move easily, facilitating electric current flow.

In more detail, the atomic structure of metals is the key to their ability to conduct electricity. Metals are made up of a lattice of positive ions surrounded by a 'sea' of delocalised electrons. These electrons are not attached to any particular atom and are free to move throughout the metal. This is often referred to as the 'sea of electrons' model.

When a voltage (or a 'push') is applied across a piece of metal, these free electrons can move easily through the metal, carrying the electric charge with them. This movement of charge is what we know as an electric current. The ease with which these electrons can move is what makes metals such good conductors of electricity.

Different metals have different levels of conductivity, depending on the number of free electrons they have available. For example, silver is the best conductor of electricity because it has the most free electrons, but it is expensive, so copper is often used instead as it is also a very good conductor and is much cheaper.

In contrast, non-metals do not have this 'sea of electrons'. Their electrons are tightly bound to their atoms and are not free to move, which is why non-metals are generally poor conductors of electricity. Some non-metals, like graphite, are exceptions to this rule due to their unique atomic structure.

In summary, the excellent conductivity of metals is due to their atomic structure, specifically the presence of free, delocalised electrons that can carry an electric charge through the metal when a voltage is applied.