‘Thy word is a lamp to my feet and a light to my path.’ Psalm 119:105
Imagine the light from glow-worms. I’ve no idea what the divine explanation is behind their glow, but without electricity they cast their tiny light into the darkness of night. God uses His light in so many ways. The extreme is the light from the sun, so bright that we damage our eyes if we stare at it. If we sun-bathe in it for too long we damage our skin. The God that made the powerful sun also made the glow-worm.
When God created light on the day of creation, He set so many things in motion. The sun guides us by day and the softer light of the moon guides us at night. How we would suffer if we had a day sun and a night sun, or a night moon and also a day moon. If would be so hard for us to function. God gives us what we need.
It isn’t only physical light that we need from God, we also need spiritual light. We need His holy light to keep us on the right path, to steer us away from temptation and to illuminate our way through life. Hell is described as a place of eternal darkness, so by definition heaven is a place of eternal light, the source of light being God Himself.