A respectable assessment of priority-based Ontic Structuralism demands an elucidation of its metaphysical backbone. Here we focus on two theses that stand in need of clarification: (1) the Fundamentality Thesis states that structures are fundamental, and (2) the Priority Thesis states that these structures are prior to putative fundamental objects, if these exist. Candidate notions to illuminate (1) and (2) such as supervenience and ontological dependence failed at this task. Our purpose is to show that grounding is the best competitor to articulate (1) and (2), and regiment such theses in a desirable unified way. Our strategy is two-fold. First, we make the case that grounding does better than ontological dependence and supervenience. Seco...