The concept of metaphor, in particular graphical (or visual) metaphor, is central to the field of information visualization. Information graphics and interactive information visualization systems employ a variety of metaphorical devices to make abstract, complex, voluminous, or otherwise difficult-to-comprehend information understandable in graphical terms. This paper explores the use of metaphor in information visualization, advancing the theory previously argued by Johnson, Lakoff, Tversky et al. that many information graphics are metaphorically understood in terms of cognitively entrenched spatial patterns known as image schemas. These patterns serve to structure and constrain abstract reasoning processes via metaphorical projection operations that are grounded in everyday perceptual experiences with phenomena such as containment, movement, and force dynamics. Building on previous research, I argue that information graphics promote comprehension of their target information through the use of graphical patterns that invoke these preexisting schematic structures. I further theorize that the degree of structural alignment of a particular graphic with one or more corresponding image schemas accounts for its perceived degree of intuitiveness. Accordingly, image schema theory can provide a powerful explanatory and predictive framework for visualization research. I review relevant theories of analogy and metaphor, and discuss the image schematic properties of several common types of information graphic. I conclude with the proposal that the inventory of image schemas culled from linguistic studies can serve as the basis for an inventory of design elements suitable for developing intuitive and effective new information visualization techniques.