What metaphor ends the play in the final song in Act 2, Scene 14?

All of the characters take necessary and important steps towards moving on, towards living the "next to normal" life referred to in Diana and Natalie's duet. Here, in the show's musical and emotional finale (its narrative climax, or point of highest emotional and thematic intensity), the narrative invokes another of its central themes, the power of light as a metaphor for hope.