Symbolism, Imagery, Allegory
There's a lot of light symbolism in Anthem, which helps to add to the mythic/religious feel of the story. The most important instance of it centers around Equality 7-2521's invention of a light bulb. Think of the scene. Equality 7-2521 creates the electric light by himself, in an underground tunnel, where it is the lone light shining in the darkness: "…in that moment nothing existed save our two hands over a wire glowing in a black abyss."(5.5). And doesn't it seem to represent Equality 7-2521's own position? He's the lone source of thought and individuality in the dark mass of his fearful and oppressive society, and the only source of hope, too.
His action of bringing forth the light "from the night of ages" (5.1) suggests his wider role as a light-bringer to his society. Originally he takes on this role for himself literally. He wants to share his invention with the others, to improve their quality of life. But towards the end of the novella, he adopts it in a higher figurative sense as well. He swears that he will be the one who will spread hope and freedom to those who suffer under the burden of collectivism. And he adopts the name of Prometheus, the god from Greek mythology who brought fire from the gods to men.
Light imagery also plays a role in Equality 7-2521's interactions with Liberty 5-3000 (just think of her shining name, the Golden One). But more important is water imagery, which characterizes Equality 7-2521's meetings with Liberty 5-3000 in both Chapter 2 and Chapter 4. See how they come together in this passage from Chapter 2:
And the drops of water falling from their hands, as they raised the water to their lips, were like sparks of fire in the sun. Then the Golden One saw us, and they did not move, kneeling there, looking at us, and circles of light played upon their white tunic, from the sun on the water of the moat, and one sparkling drop fell from a finger of their hand held as frozen in the air. (2.15)
Water is suggestive of birth and rebirth, of new beginnings and the "washing away" of the old. Think baptism. Light and Water complement each other. You could think of Liberty 5-3000 playing water-bearer (she does literally, in Chapter 4) to Equality 7-2521's light-bearer.