Designers that adopt composite materials for the skin of aerospace structures must verify that their systems guarantee an equivalent level of protection against lightning strikes with respect to the ones that adopt traditional metallic skins. In particular, the design must ensure that lightning strikes do not cause critical damages to structures, systems, and payload. This section introduces the references for requirements and specifications of lightning protection issues involving aerospace systems. Moreover, the physics of the lightning is documented, that is, the way a strike can be generated. Also the analytical models of the lightning are reported considering all the significant terms involved. The effect of lightning strikes on the aerospace structures is discussed. They can be divided into two main categories, such as direct effects, that is, the ones that produce a direct physical damage on a vehicle, and indirect effects, that is, the ones produced by the currents induced by the magnetic fields of the strike that are determined in proximity of the skin of an aerospace platform. Finally, the methods adopted for protection of aerospace systems having skins made of composite materials against the effects of lightning strikes are presented, considering both conductive and nonconductive types of composite.