Lightning conductors are made up of metal rod, which is fixed up on the top of the building and is connected to a copper plate placed inside the ground. When lightning strikes the building the metal rod which is a good conductor of electricity attracts it and the current produced by the lightning passes through this rod to the conducting wire and finally reaches to the ground where the copper or aluminum plate is placed. The current then dissipated inside the earth. This is how the lightning conductors on the buildings prevents from damage due to lightning.