Taking the assumption that understanding metaphors requires activation of conceptual mappings between the involved concepts, the paper tests whether mappings are indeed in use during metaphor comprehension. The paper also tries to find an answer to the question of what the concept mapping really means as a cognitive process with Event-Related Potentials. Participants in the test had to read literal, conventional metaphorical, novel metaphorical, and anomalous target sentences preceded by primes with related or unrelated mappings. While Experiment 1 used sentence-primes to activate related mappings, Experiment 2 used simile-primes to induce comparison thinking. As a result of both experiments, researchers believe that mapping as a process occur in metaphors, and that the ways in which it can be facilitated by comparison differ between conventional and novel metaphors.