In this article, we examine the role that different participant structures can play in supporting inquiry-based science learning. We frame mastering scientific inquiry as mastering the "what," "why," and "how" of the cultural tools that scientists employ. We present a participant structure we call the teacher as partner and show how it renders the what, why, and how visible while establishing symmetry between teachers and students. We draw on Wertsch's (1998) distinction between mastery, gaining proficiency with a cultural tool, and appropriation, making a tool one's own, to show that the partner participant structure contributes to both. Thus, we propose that the teacher as partner serve as a generative metaphor for inquiry teaching in responding to current calls to consider identity formation as well as subject-matter learning in formal schooling. We hope that it invites research on instructional moves that can demystify the process of science and help students identify themselves as ratified participants who can contend with scientific issues as citizens.