For example, soybean is mainly used to refine soybean oil, and rapeseed oil is a competitive commodity that can be replaced by each other. If soybean oil is in short supply and the price rises,
Some consumers will buy rapeseed oil instead, which will drive the price of rapeseed oil to rise, and there is a price linkage in the same direction between them.
Similar futures trading varieties include gold, platinum and silver, corn, wheat and oats, copper and zinc, etc.
Commodities with complementary functions do not seem to be common in commodity futures.
Automobile and gasoline are typical commodities with complementary functions.
With the increase of gasoline price, the cost pressure of consumers using cars will increase, which will bring pressure to the sales of cars.
There is a reverse price linkage between them. (Personal understanding, for reference only)