In order to exchange trade goods with a partner, you have to have something that that partner wants. The European traders had nothing that the Chinese wanted. Therefore, they had to pay for their silk and porcelain in gold and silver.
When Europeans first came to trade with China, the Chinese saw them as barbarians. The Chinese saw themselves as the “Middle Kingdom,” a place that was superior to the rest of the world. They felt that their technology and culture was superior to everyone else’s. Therefore, they had no interest in anything that the Europeans tried to trade with them. They would only accept gold and silver.
This became a problem for the Europeans because it was draining their reserves of gold and silver. This is why they eventually decided to start trading opium to the Chinese in exchange for silks, porcelains, and tea. This led to a great deal of conflict and, eventually, the Opium Wars.