Contact, friction, and fracture are fundamental processes governing the emergent (mechanical) behaviors of various complex (material) systems, from as large as tectonic slip to as small as third-body wear. In this talk, we briefly discuss (1) challenges in understanding the (nonlinear) mechanics of these processes, specifically focusing on those designed into metamaterials, and (2) novel engineering applications they may lead to, specifically in the context of enabling sustainable interaction between the natural and built environment.