Since Jesus is the light of the world we need to accurately reflect His light to others. When Jesus died on the cross He gave all men light and everlasting life; in hell for those who do not submit to Him and in heaven for Christians.
We are the light to the world. Because we are Christians, we should not blend in with the world, as we so easily tend to. To reach others we don't have to be like them. In 1 Peter 2:9 "But you are a chosen race, a royal priesthood, a holy nation, a people for God's own possession, so that you may proclaim the excellencies of Him who has called you out of darkness into His marvelous light; for you once were not a people, but now you are the people of God; you had not received mercy, but now you have received mercy." We are a chosen people. We will be different than the world if we are like Christ. We DO NOT have to be like the world to witness to them.