Trading scrap metal for street cigarettes means selling useless furniture for a full meal. According to relevant information, junk is abandoned furniture, and the smoke on the street refers to the restaurant on the street, so it means selling the abandoned furniture and changing it to a delicious meal in the restaurant on the street. A restaurant is a shop that sells food for human consumption. An example is Ai Wu's "A Lesson of Philosophy of Life": The sound of small dishes in restaurants and the strong smell of oil smoke in the street tempted my tongue and slipped to my upper and lower lips and licked it twice.