God is referred to be the light of the world because He illuminates our life and gives us direction, clarity, and truth. We stumble and get lost in the dark, but when God's light shines on us, we can see the way He has planned out for us.
He is the salvation of mankind because of His love and atonement, which frees us from sin and grants us eternal life. We would be lost and condemned in the absence of His kindness and mercy. Knowing that He loves us without condition allows us to achieve true peace and restoration when we embrace Him as our Savior.