Forging is best described as:

Forging is best described as shaping metal through compressive forces, which is essentially what occurs during the forging process. This method involves applying pressure to metal, thereby deforming it into the desired shape without melting it. The process can take various forms, including open-die forging, closed-die forging, and others, each utilizing these compressive forces to achieve different shapes and structural properties in the metal.

The primary aspect of forging distinguishes it from other methods of metalworking, such as casting, which involves melting metal and pouring it into molds, or rolling, which reduces the thickness of metal. While forging may change the thickness of the material as it is formed, its defining characteristic is the application of compressive forces to reshape the metal rather than simply thinning it. Additionally, the option regarding separating metals using gravity is unrelated to the fundamental principles of forging as it pertains to shaping metal. Thus, the most accurate representation of the forging process is through the application of compressive forces to shape the metal.