The Lightning Element is the Sheild Arm of Light. It was originally the Sword Arm, but was considered too cruel to use as a weapon, though it could be still used as one. It was claimed by Darkness before the First Heavenly War, and was taken by Light during the First Heavenly War.
Its polar opposite is Thunder, but both occur in nature at the same time making them dependent on each other. Lightning is an element of speed. Lightning moves very quick and never stops, it also generates electricity, making it an element of electricity, and is one of the causes of fire, which leads to believe a connection between them.