Mobilizing individuals to fight together for justice is both an interpersonal and a cultural act. Yet the most widely used explanations of collective action overlook the cultural work that precedes the core components of micro-mobilization—communicating opportunities, transferring resources, and creating resonant meanings or frames. I examine this cultural work using ethnographic research on the fight over mountaintop removal coal mining in central Appalachia. I discovered the presence of cultural matching and mismatching in recruitment and enrollment: Social movement organizations tended to recruit participants who already fit culturally with the existing group's mobilizing style—a set of understandings, tactics, and modes of interacting that cohered around a group's theory of social change; local residents tended to join and support an organization on the congeniality of its mobilizing style. Mobilizing styles had semiotic import, most noticeably by placing social movement organizations on a relationally-defined scale of insider–outsider. I also observed cultural adaptation. Groups based on the style of community organizing changed to become more like local residents, while groups based on the style of activism did not. Reciprocally, I observed cultural breaks in which organization members or local residents abandoned the other. As a response to this social movement, the coal industry actively attempted to produce a culture into which it already fit, but elites also accented and adapted to local culture as a way to gain legitimacy, create togetherness, and convince local residents that the industry was an "insider," unlike "outsider" challengers. Overall, cultural matches and matching created connection, promoted trust, and nourished mobilization. Cultural mismatches and mismatching created disconnection, interfered with frame alignment, exacerbated community tension, and hindered further collective-action efforts. This study provides a more robust account of culture in mobilization and sheds light on a key micro-social process that helps to account for why social movements sometimes fail, or never even begin.