Why is the Torah compared to light? Because it tells us the place of everything.
Because, in reality, there's no need to change the world. Everything is here.
Everything has its place, and in that place, it's good. Overall, it's very good, a beautiful world. All it needs is a little light.
What is light? Light neither adds nor takes away. It simply reveals the meaning and purpose of everything it shines upon.
Think about your own home. In the dark, there's no way you can tell what belongs in your closet and what belongs in the washing machine, what's ready to be used and what needs repairing. Instead, things that could be washed and repaired are rejected and discarded, and your most valuable possessions can become your greatest dangers.
Light a small candle and a dangerous place becomes a home. With each additional light you add, you suddenly become richer and more blessed.
Likewise, this world is meant to be God's house. The Torah is light. Let it shine brightly and heal the world.
Torat Menachem 5742 vol. 3, p.1626; Ibid 5748 vol. 4, p. 175.