ANswer is Nationalism
World-systems theory (also known as world-systems analysis or the world-systems perspective),[1] is a multidisciplinary, macro-scale approach to world history and social change which emphasizes the world-system (and not nation states) as the primary (but not exclusive) unit of social analysis.[1][2]
"World-system" refers to the inter-regional and transnational division of labor, which divides the world into core countries, semi-periphery countries, and the periphery countries.[2]Core countries focus on higher skill, capital-intensive production, and the rest of the world focuses on low-skill, labor-intensive production and extraction of raw materials.[3] This constantly reinforces the dominance of the core countries.[3] Nonetheless, the system has dynamic characteristics, in part as a result of revolutions in transport technology, and individual states can gain or lose their core (semi-periphery, periphery) status over time.[3] This structure is unified by the division of labour. It is a world-economy rooted in a capitalist economy.[4] For a time, certain countries become the world hegemon; during the last few centuries, as the world-system has extended geographically and intensified economically, this status has passed from the Netherlands, to the United Kingdom and (most recently) to the United States.<span>[3]</span>
Metal would be your answer as it's a permeable substance.
hope it helps!
