I'm don't think there are many things more beautiful than sharing candlelight in a dark church and singing "Silent Night" together. That's how our school's annual Vespers service ends (well, sort of: except for the recessional hymn. And the ten minutes of carols played by the combined instrumental ensembles), and it's how Christmas Eve services always ended when I was growing up. It just works on so many levels.
In the first place, it's visually beautiful. All of these human faces, each illuminated by a single candle, which combine to give a gentle glow to the whole sanctuary. Gorgeous. In the second place, it sounds wonderful, especially on the last verse when the organ drops out and it's just human voices singing together.
But it's also a wonderful metaphor for so many things. One candle's flame is shared with another candle, and then another and another, and where there was darkness, gradually there is light. It's the light of knowledge, whether that's the knowledge of a Savior born two thousand years ago or the knowledge of how the world works, illuminated through evolution or physics or psychology or literature. For the light of that knowledge to grow, it has to be shared in that painstaking process from one person to another (and sometimes, you get burnt a little for your troubles). It's the light of love, of compassion, of human connection, passed from one person to the next to the next, until it lights up a family, a neighborhood, a community, a nation, a world.
At least, that's the hope.