What metaphors are used in Missing May by Cynthia Rylant?

The Chevy is a beat up old pick-up truck that Ob held onto years after it first broke down. All her life, Summer wondered why he had kept the broken down truck, but on the day of May's funeral, she realized why. Ob spent the night in the pickup, and Summer realized he saved it for a time in his life when he would need to sit somewhere quiet and truly feel alone: a metaphor for solidude.