One way to determine the relative activity of the metals is to place a piece of solid metal into a solution of another metal. The more active metal will either become dissolved or remain dissolved. The less active metal will either precipitate from solution or remain undissolved. So, our experiment is designed to test the metals against one another, "head-to-head", so to speak. It is useful to think of the metals as battling one another to stay (or become) dissolved.