This is the message at have heard from him and proclaim to you: God is light; in him there is no darkness at all.
This is it. Of all the things that Jesus said, all he did and taught and showed; every parable, symbol, story, miracle points to this one glorious truth: God is light.
Why light? Why use that metaphor? (if metaphor it is because God does indeed dwell in unapproachable light - 1 Tim 6.16) Why not God is truth, God is holy, God is good? For he is. Does light somehow encapsulate all of the above? The pure, white heat of holy fire that burns up every shred of darkness in our hearts, the thing by which we see all else, the One who lights our path (Isaiah 42.16) so that we need not stumble, the opposite of all that is evil, all the injustice that is cleverly concealed...
Or is Jesus' message more simple than that. God is light. He is not who you have been told he is. He is not angry or tyrannical or fickle. There is no shadow of turning in him. (James 1:17) He is the beauty of that first pale dawning light glimmering on the horizon after a long winter's night; he is the golden splendour of late afternoon sun painting everything with its glory; he is the candle flame that penetrates the power cut. He is the light of the world. Those who follow him need never fear the dark again. (John 8:12)