Michael Porter's Five Forces model analyzes competitive rivalry and industry profitability. The model examines five forces: threat of new entry, power of suppliers, power of buyers, threat of substitutes, and rivalry among existing competitors. When rivalry among competing firms intensifies, industry profits decline and the industry may become unattractive. Porter developed the model to understand why some industries are more profitable than others based on structural factors like barriers to entry, economies of scale, and product differentiation.