There are two kinds of materials for making cans: one is aluminum, and the other is tinplate. The consumption of aluminum metal materials used in packaging containers in the United States reached 1,992,000 tons in 1998, an increase of 2.24% over 1997, making it the second largest consumer market, accounting for 21.6% of the annual aluminum consumption. In the United States, aluminum sheets have always been used as materials for cans, and about 40% of aluminum sheets are used in the production of cans every year. The strong opponent of aluminum in the packaging industry comes from PET materials. PET materials can be made into strange appearances through injection molds, while aluminum materials are relatively difficult. However, there is a big difference in the prices of the two materials. PET is affected by the price of oil. Aluminum can be recycled through its own recycling, reducing material costs, and is valued by environmental organizations.