As a stroke moves through the air, it generates tremendous heat that unites nitrogen and oxygen to form nitrates and other compounds. These compounds fall to the Earth with the rain. In this way, the atmosphere is able continually to help replenish the supply of nutrients that soil needs to produce plants. The attraction of tall structures for lightning has been known for centuries. This is easily explained by modern electrical theory.
Lightning is an electrical current that tries to bridge the air gap between the ground and a cloud.
Thus the positive ground charge will concentrate at the highest point on the ground, and the stroke will usually be between that point and the cloud. For this reason, a lightning rod, or shield, is placed higher than all other objects near it. A shield may be a single pole set in the ground or a group of masts supported in a framework that completely surrounds a building. The shield provides a good target for a lightning stroke and thus protects other nearby structures. Lightning normally strikes the tallest object in its range.