Jesus uses two domestic images, salt and light, to teach the disciples how important they are in sharing his mission.  Notice that Jesus uses an emphatic phrasing: “You are…” Not,  you can be, or you might be, or maybe your will be.  No, he is very direct in naming them as salt and light, they are change agents.  Just as salt adds flavor to food and light dispels the darkness, so will they transform the world by their witness and their good deeds.    In accepting this identity we bring glory to God.