The Scriptures tell us that God is light but not many people understand the concept. We think of light as energy, and therefore we assume that God is a force or energy field. To say that God is light is equivalent to saying that a truck is metal. When we think of God we should be thinking of his essence.
God is light because when darkness comes near him, it immediately is transformed. Darkness cannot transform light, but light always can transform darkness. Humans also have the capacity to transform darkness because they were created in the likeness of God, and they too are light. But they have a choice of whether or not they will embrace the darkness or transform it. If a human being chooses to embrace the darkness, they become like the darkness. They lose their ability to transform it.
Knowing that one is light enables a person to persevere through any form of darkness, confident that eventually the darkness will succumb to the light. The darkness in our world also eventually will succumb to the light. It is only a matter of time before we each recognize that all that is required is a decision to be who we are at our core, to be the light of the world, and the darkness in our world will dissipate.