The lost thing in the movie is a giant and red monster. And this story is talking about a man takes the lost thing where it belongs. However, in my view, the lost thing means something else. Creativity or happiness. The reason is because he said that people are too busy to notice the lost thing and most of people in the movie look tired and unhappy. People in the movie lack a relationship and connection, which made life more colorful to others. Maybe the director wants to tell people don’t work or live as a machine or robot. Be creativity or be interesting to something. And there is a funny or ironic thing that the lost thing or other things- monsters looks like some creatures mixed with machine and animals but those things do not live as machine and they know to play or enjoy. In the other hand, human in this movie acts like machine.
Also, he says that he can’t see the lost thing when he grows up and in the end of this movie, he is sitting with them —- most of people who looks in a bad mood. However, before the ending, the man is just doing what he interests to. It may means people may lose their creativity or personality when they grow up and they just become a part of the public.
On other hands, in the movie we can easily find that the world buehind the wall is more primitive compared with that metropolis the boy lives in. In the metropolis, although people hardly talk to each other at all, they do works effectively:every bus, cars are following the road to keep the city busy but methodical. That states that to make life better, there are something that we must give up, and in this move it is characterized as “The Lost Thing”, a machine contains the part people give up for a better life like playing,close relations and children’s simplicity. In the end of the movie we can see the boy grew up, maybe he grew up like a man like his father, unconcerned about everything. He never find his “lost thing” back, he also became successful and find a role in the metropolis. Thus I think if people want to make life better, this is something that they have to give up, to make them stronger.