How is lightning form ? Water and ice move around inside the cloud; forced up by warm air currents, down by gravity, and compressed in the cloud. Just as rubbing a balloon can create static electricity, the particles in the cloud become charged. It's not clear how it happens, but charges separate in the cloud.
Air does not conduct electricity in the way that metals do. We normally think of conductors as metals with free electrons that move easily throughout the whole metal. Small voltages move the electrons and a current can flow.
In the case of air and many other materials there are electrons present, but they are firmly bound to individual atoms and molecules and cannot move about the way the free electrons do in metals...yeah now it`s proved that if air become good conductor then lightning will occur