From Destinypedia, the Destiny wiki
Solar is one of several known manifestations of the Light, along with Void and Arc. It is related to combustion, heat and nuclear fusion, and can be wielded by Guardians to generate flames and other heat-related phenomena. It is also one of four classes of elemental damage common to all Guardian weapons.
Solar energy can be integrated into vehicles such as sparrows, even certain clothing that have a program to it is capable of enhancing the use of Solar. There are even places that can refine items from solar energy.
Warlocks known as sunsingers buff themselves using solar light to rapidly increase their grenade recharge rate and to gain other various benefits. In Destiny 2 this ability was replaced with Dawnblade.
List of appearances