"God is light." (1John 1:5)
To be clear, light is a very common metaphor for G-dliness in Judaism and the quote from John resonates as a perfectly fine metaphor, rather than a literal assertion of equivalence.
[0] "וַיֹּ֥אמֶר אֱלֹהִ֖ים יְהִי־א֑וֹר וַֽיְהִי־אֽוֹר"
The fact that someone reading Genesis would have had a more accurate conception of the origin of the universe, prior to big bang becoming popularized very recently in the grand scheme of things is noteworthy.
God sent a man, John the Baptist, to tell about the light so that everyone might believe because of his testimony. John himself was not the light; he was simply a witness to tell about the light. The one who is the true light, who gives light to everyone, was coming into the world.
He came into the very world he created, but the world didn’t recognize him. He came to his own people, and even they rejected him. But to all who believed him and accepted him, he gave the right to become children of God."(John 1:5-12)