I designed a metal product. How can I apply for a patent?

That depends on what kind of patent you apply for. There are three kinds of patents in China: invention patent, utility model patent and design patent. Invention patents shall undergo preliminary examination and substantive examination, and utility models and designs shall be authorized to be announced only after preliminary examination. Invention patents shall submit requests, specifications, summaries of specifications and claims, and if necessary, drawings of specifications shall be attached. The patent for utility model shall submit the request, the patent claim, the specification, the appended drawings of the specification, the abstract of the specification and the appended drawings of the abstract, and the patent for design shall submit the request, the picture or photograph of the design.