The designers of human-computer interfaces use metaphors to transfer functions and operations of a known concept onto a new, abstract function in a technical system. After defining the concept of metaphor, we derive a method to find and explore new ones. The focus of the essay is on designing graspable user interfaces. While most of the literature takes a repertoire of metaphors for granted, we utilize materials and substances from daily life to investigate how to interact with them. This method is illustrated by examples of student-based research.