God takes human form
John opens his gospel with these mysterious words:

“In the beginning was the Word, and the Word was with God, and the Word was God. He was with God in the beginning. Through him all things were made; without him nothing was made that has been made. In him was life, and that life was the light of all mankind. The light shines in the darkness, and the darkness has not overcome it.” John 1:1-5 NIV

Is there light if there’s no darkness?
Your immediate response is “Of course there is!”
But it isn’t the light that causes us to act, except possibly reaching for a pair of sunglasses or shades. Now that we’re in Standard Time, the darkness is mostly complete by 4:30 PM. And then we appreciate the light.
What happens when it gets dark?
We turn on lights. Solar lights come on automatically. Even our hot tub has lights!
So God sent Light into the darkness of the world. Jesus Christ.

What about Christmas lights?
Lights in one form or another are integral to celebrating many holidays, Christmas among them. There are trees full of lights. We put automatic lighting candles in our windows to replicate the colonial experience of celebrating the birthday of the King of kings. Lighted wreaths. Outdoor lights. Lighted blown up figures.
The dark of the season is overcome by the lights, signifying the light, Jesus Christ, coming into the world.