Most take ferrous metal (steel, iron, cars and appliances) by the ton and non-ferrous metal (copper, brass, aluminum, stainless) by the pound, at prices that change with the commodity market. Sort metals before you go; clean, separated copper and aluminum pay more. Bring a photo ID, which most states require for scrap sales.
Data: Overture Maps Foundation places data (CDLA Permissive 2.0) and each yard's own website. Listings change; confirm details with the yard before you go. How this directory is built.