Cognitive linguistic and semiotic accounts of metaphor have addressed similar issues such as universality, conventionality, context-sensitivity, cross-cultural variation, creativity, and “multimodality.” However, cognitive linguistics and semiotics have been poor bedfellows and interactions between them have often resulted in cross-talk. This paper, which focuses on metaphors in Greek street art, aims to improve this situation by using concepts and methods from cognitive semiotics, notably the conceptual-empirical loop and methodological triangulation. In line with the cognitive semiotics paradigm, we illustrate the significance of the terminological and conceptual distinction between semiotic systems (language, gesture, and depiction) and sensory modalities (sight, hearing, touch, smell, and taste). Thus, we restrict the term multimodality to the synergy of two or more different sensory modalities and introduce the notion of polysemiotic communication in the sense of the intertwined use of two or more semiotic systems. In our synthetic approach, we employ the Motivation and Sedimentation Model (MSM), which distinguishes between three interacting levels of meaning making: the embodied, the sedimented, and the situated. Consistent with this, we suggest a definition of metaphor, leading to the assertion that metaphor is a process of experiencing one thing in terms of another, giving rise to both tension and iconicity between the two “things” (meanings, experiences, concepts). By reviewing an empirical study on unisemiotic and polysemiotic metaphors in Greek street art, we show that the actual metaphorical interpretation is ultimately a matter of situated and socio-culturally-sensitive sign use and hence a dynamic and creative process in a real-life context.