Now, I fully believe in the literal interpretation of Genesis, but I think there may be some deeper meaning here as well. Think about it. God called for light before He went any further with Creation. The constant battle we face in this fallen world is light versus darkness, good versus evil. We often associate light with goodness.
In saying, "Let there be light" it's almost like God was saying, "Let there be goodness." "Let My people shine." "Let My love light the world."
1 John 1:5 says, "God is light and in Him there is no darkness at all."
After God said, "Let there be light," the verse goes on to say, "and there was light." (Psalm 33:9 also says, "For He spoke, and it was done; He commanded, and it stood fast.") When God speaks, it actually happens. And there really is light in this dark world.
You are the light.