God did not just create light, He is the light. Those who follow where God leads are in the light, those who reject God are in darkness, whee all manner of evil spirits dwell.

This was symbolized at the time of the Exodus when God allowed darkness to fall over the whole lad of Egypt for three days, while the Israelites in Goshen had light.

When God led the people out of Egypt, He was a light for them, but to the Egyptians He was a dark cloud that prevented them from coming near. A little later, Moses went up the mountain, through the thick cloud that hid him from the people camped around the mountain. But when he reached the top of the mountain he was in the light of God’s presence, so much so that when he came down the mountain his own face shone so brightly the people could not bear to look at him.

But the natural tendency of humanity is to prefer darkness, so that others do not see what we do, even though God has promised that He will forgive us when we confess our sins and open them up to the light.

The Old Testament warned the people of Israel:
And thou shalt grope at noonday, as the blind gropeth in darkness, and thou shalt not prosper in thy ways: and thou shalt be only oppressed and spoiled evermore, and no man shall save thee. Deuteronomy 28:29
And I will bring distress upon men, that they shall walk like blind men, because they have sinned against the LORD: and their blood shall be poured out as dust, and their flesh as the dung. Zephaniah 1:17

It also promised that one day light would come into the world in a new and glorious way:
Arise, shine; for thy light is come, and the glory of the LORD is risen upon thee. For, behold, the darkness shall cover the earth, and gross darkness the people: but the LORD shall arise upon thee, and his glory shall be seen upon thee. And the Gentiles shall come to thy light, and kings to the brightness of thy rising. Isaiah 60:1-3

Jesus was that light and all four gospels tell how the forces of darkness conspired against Him. Yet he continually demonstrated His power over the realm of darkness by healing diseases, casting out demons and giving sight to the blind.

There were sinister forces behind those waves on the sea of Galilee that threatened to destroy the disciples, and even Jesus Himself, if possible. In one incident, Jesus spoke to the wind and the waves and their power was gone. In another, He came walking on the waves, showing that they had no power over Him.

And yet, the forces of darkness did eventually appear to triumph, having Jesus nailed to a Roman cross where He died. He was declared innocent by the Roman trial, yet the religious leadership demonstrated just how thoroughly they were controlled by the realm of darkness by insisting that He be crucified.

Their plan backfired. The tomb could not hold Him. Fifty days later, after our risen Saviour had departed from this world, His followers received power to become bearers of the light. They numbered 120 at that time, according to Acts 1:15. On the day of Pentecost, tongues of fire appeared upon each of them and they began to boldly preach the gospel. Since that day, the light of the gospel has spread into all the world.