What are good conductors of heat?

Good question. We know that a conductor allows electricity to move through it. But why is that? Conductors have a source called mobile electrons that go side to side inside the conductor itself when...

In general, good conductors of heat are good conductors of electricity.

Yes, because they are metals insulators are nonmetals.

This is usually true for metals. It is not usually true for nonmetallic substances, however. Diamonds conduct heat much better than copper, but are electrical insulators.

This is because valence shell of metals contains free electros which enables them to conduct heat and electricity.