Lighting is a massive electrostatic discharge cause by unbalanced electric charge in either the atmosphere or in clouds.
Lightning is probably third or fourth most deadliest natural event know to ponies. Its completely random in its strikes. Un-bias in it target and its kill in the first shot. Those who are lucky enough to survive don't enjoy the feeling of it. Lightning is a force that shouldn't be trifled with for the safety of others. Not something that should be given to a colt who is barely 10 years old and is basically new to the world entirely.