“Again Jesus spoke to them, saying, “I am the light of the world. Whoever follows me will not walk in darkness, but will have the light of life.” (John 8:12 ESV)

Light is an interesting thing

Light is not like darkness because darkness does not exist (it’s the absence of light). Darkness cannot extinguish light, but light can extinguish darkness. You can reflect light, like the moon does, or carry it in your hand and shine it onto things, as with a lamp or flashlight.

“The light shines in the darkness, and the darkness has not overcome it.” (John 1:5)

Therefore

“For at one time you were darkness, but now you are light in the Lord. Walk as children of light.” (Eph. 5:8)

“But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light.” (1 Peter 2:9)