Lightning protection systems are used to prevent or lessen lightning strike damage to structures.
A lightning protection system provides a low-impedance path for the lightning current to lessen the heating effect of current flowing through flammable structural materials.
If lightning travels through porous and water-saturated materials, these materials may literally explode if their water content is flashed to steam by heat produced from the high current. This is why trees are often shattered by lightning strikes.
Because of the high energy and current levels associated with lightning (currents can be in excess of 170,000 amps, 170kA), and the very rapid rise time of a lightning strike, no protection system can guarantee absolute safety from lightning.
Lightning current will divide to follow every conductive path to ground, and even the divided current can cause damage.
Secondary "side-flashes" can be enough to ignite a fire, blow apart brick, stone, or concrete, or injure occupants within a structure or building.