You generate an arc of lightning between two targets. The lightning deals 1d6 points of electricity damage per caster level (maximum 15d6) to both targets and any creatures in a line connecting them. The spell fails if there is no line of effect between the targets. Lightning arc sets fire to combustibles and damages objects in its path. It can melt metals that have a low melting point, such as lead, gold, copper, silver, or bronze.