As metaphor is a conceptual mapping from the source domain to the target domain, it seems reasonable to ask what typical source domains and what typical target domains are. The cognitive answer is that the source domains are typically concrete and physical while the target domains are typically abstract and nonphysical since human conceptual systems "contain mappings of inference patterns from typically more concrete domains to typically more abstract domains. As a basic cognitive structure, metaphor allows us to understand relatively abstract or inherently unstructured subject matter in terms of a more concrete, or at least a more highly structured subject matter. In fact, many subject matters such as time and emotion can only be comprehended via metaphor. In short, metaphor is the main mechanism through which we comprehend abstract concepts and perform abstract reasoning.

"To function as a source domain for a metaphor, a domain must be understood independent of metaphor." It must be something concrete and physical about which man can develop knowledge directly on the basis of his bodily experience. Therefore, for our conceptualization of abstract categories we rely on the basic experiences of the general classes of objects, organisms and persons. This object/organism/person view of the world facilitates the cognitive handling and manipulating of abstract categories. Thus many abstract concepts are comprehended as objects, animate entities or human beings such as the conceptual metaphors IDEAS ARE OBJECTS, IDEAS ARE ANIMATE BEINGS OR PERSONS. The reason we can understand abstract categories in terms of these general classes is that the specific way we interact with instances of the three classes is extremely familiar to us, and this intèraction provides the source for the metaphorical mappings.

While source domains are usually those concrete, physical and tangible categories comprehended directly on the basis of bodily experience, target domains are often those abstract, nonphysical and intangible categories that are not easy to understand directly. Among the target domains are anger, hate, happiness, love, lust, argument, communication, ideas, theories, life, death, quantity, authority, power, evaluation, social structure, event structure, etc.