The substances which allow the electric current to pass through them are called conductors. There are two types of conductors.
(i) METALLIC CONDUCTORS
The passage of electric current in conductors is due to the movement of free electrons. Also the conducting material does not undergo any chemical change. A current of electricity is a stream of electrons. Examples; Metals like Cu, Al etc. Non-metals like graphite.
The flow of current in conductors is due to the movement of ions towards oppositely charged electrodes. Such conductors result in chemical changes at the electrodes. For Examples: Solutions of acids and bases, fused salts, aqueous solutions of salts such as NaCI.