To a percussionist, a gong is a very specific instrument.

Gongs are typically metal alloys that consist mostly of copper and/or brass. Their purpose is to produce a long sustained sound that is somewhere between a crash and a ring. They are made in a large saucer-like shape. The part of a gong that most people overlook, is the center of the gong. The center should protrude towards the hitting side of the metal. This is essential, because if that protrusion does not exist, then it isn't considered to be a gong by percussionists. If the center is flat, then we refer to the instrument as a tam-tam, and it is not a gong at all.

Gongs are almost used exclusively in the "classical" music genres. Gongs are generally used for dramatic or dark sections of symphonic pieces.

Gongs may be tuned, or untuned (meaning they are sometimes designed to produce a specific note, ie, b-flat). They are more commonly played by striking, but are sometimes scraped with a metal rod since gongs are textured similar to a vinyl record.

China, which is generally accepted as the origin of the instrument, used gongs similarly to the way medieval Europe would use church bells. It was considered a tool for communication and announcements, but nowadays it is known as a sophisticated symphonic instrument.