Imagine a coffee maker that subtly references the serving gesture of a butler or a car that explicitly mimics the sleek and streamlined form of a jet plane. Such metaphors are frequently used by designers as a means to render the values and meanings they want to assign to a product into a physical form. By their nature, metaphors build meaningful relationships between two distinct entities, which urge us to see things in a new light. For this reason, designers resort to metaphors to exhibit original and aesthetic solutions to design problems. Still, so far the use of metaphors has not taken up the importance in design academia as it did in design practice. In this thesis, it was aimed to propose a structured means to incorporate metaphor in design research by investigating a product metaphor’s characteristics and the peculiar type of thought process that generates it. Through four empirical studies conducted with designers, we gradually built a framework that accounts for the processes underlying product metaphor generation and examine the success of the decisions taken in this process. On the basis of the results, we also formulated a set of practical recommendations to designers, which they may use as an inspiration for creating good metaphors.