How does the author use metaphor in the nonfiction book, Things My Son Needs to Know About the World?

In the essay titled, What you need to know about stuff, Backman uses the concept of "stuff" as a metaphor for materialism. He explains that people accumulate a huge amount of stuff because they are told that they need more stuff, and that stuff then requires the accessory stuff. This is especially true for parents who want the best of everything for their children and feel pressure to provide their children with more in life than they had. Backman stresses to his son not to become attached to the stuff he has in his life, and that he must not let material items become more important than the people he surrounds himself with.