The substance is called a conductor . Some conductors are better than others, but none are perfect, and all resist electron flow to some extent. When electron flow is resisted, some of the energy in the electrons does not travel through all the way. Because energy is conserved, the energy that was moving the electrons forward is converted to heat energy. It can also be converted to light energy, as in the filament in a light bulb.
Some substances are better conductors than others.
There are certain substances, which when cooled to near absolute zero offer almost no resistance. Those are called superconductors .