  The article is devoted to electromagnetic phenomena in the atmosphere. The
set of experimental data on the thunderstorm activity is analyzed. It helps to
identify a possible physical mechanism of lightning flashes. This mechanism can
involve the formation of metallic bonds in thunderclouds. The analysis of the
problem is performed at a microphysical level within the framework of quantum
mechanics. The mechanism of appearance of metallic conductivity includes the
resonant tunneling of electrons along resonance-percolation trajectories. Such
bonds allow the charges from the vast cloud charged subsystems concentrate
quickly in lightning channel. The formation of metal bonds in the thunderstorm
cloudiness is described as the second-order phase transition. A successive
mechanism for the process of formation and development of the lightning channel
is suggested. This mechanism is associated with the change in the orientation
of crystals in growing electric field. Possible consequences of the
quantum-mechanical mechanism under discussion are compared with the results of
observations.
