Generally speaking, it is to study the relationship between supply, that is, the relationship between production quantity and consumption quantity. There are too many things to elaborate on. Take steel as an example, in terms of production: the prices of raw materials such as iron ore and coke (including water and electricity), transportation prices, production technology and so on. Consumption: production and sales of iron and steel enterprises, real estate boom, national purchasing and storage, etc. Think carefully ... the factors that affect the price of iron ore and coke ... If you are interested in steel, you can visit the steel market more, and the spot dealers will be happy to give you lessons. Copper ... If you are in the Yangtze River Delta, it is more convenient to contact the spot chamber of commerce. If it is in other areas, it is enough to know about it, but it will be very inconvenient to make copper.

Personal suggestion: to study agricultural products, first, it is in line with the external market, and second, the transaction volume is relatively large and the price is not high.