What does John 3:29 mean?

'The groom is the one who gets the bride. The friend of the groom just stands by and listens, and he’s thrilled to hear the groom’s voice. That’s how I feel—my joy is complete.' John 3:29 - Modern Text Bible

(John uses a wedding metaphor: he’s like the best man, happy to see the groom (Jesus) take center stage. He’s not jealous—he’s glad.)