Light of the world 
Why is Jesus Christ called the Light of the World?
Jesus went to the temple during the Feast of Tabernacles. The temple was illuminated by four very large chandeliers and its light could be seen from a great distance. Here, He rescued the woman from being stoned for adultery and then proclaimed to those who observed the event:
Juan 8:12–36. "I am the light of the world: he who follows me will not walk in darkness, but will have the light of life."
Source
Darkness, in a spiritual sense, often refers to sin or confusion about the truth. Just as in life darkness can hide evil or distort what is real, in the spiritual world, it can distort the truth or hinder the vision or understanding of the truth. However, God created both day and night, and He does not expect us to live in darkness. He wants us to live our lives in light, and that light comes from the Savior.
Jesus Christ came to earth to fulfill the prophecy and to fulfill a promise he made to us before we were born; He promised to come and redeem us from our sins. Prior to this, He taught the gospel, helping those who heard to see beyond the Law of Moses into the new and higher laws of love.
For more information, check his blog:
https://steemit.com/celestialchallenge/@sirknight/sirknight-s-daily-celestial-challenge-new-for-all-steemians
Note: @sirknight started a contest and its daily topics are:
Sunday - light.
Monday - darkness.
Tuesday - animal kingdom.
Wednesday - Structures.
Thursday – ForcesinNature.
Friday - LoveBeautyFreedom.
Saturday - Agriculture.