If you’re choosing between metal and wood for a street bench in a coastal area, I’d frame the decision around salt air, humidity, sun, and maintenance. In my experience, metal is often the safer default — but only if you pick the right alloy or coating.
Marine-grade stainless steel (316) and aluminum are the real winners. They resist the salt-laden air far better than ordinary steel or iron. Powder-coated aluminum or stainless stands up well, though scratches need touch-ups to prevent hidden corrosion. Avoid bare carbon steel and cheap cast iron unless they’re hot-dip galvanized and maintained, because coastal salt spray will eat through them quickly at bolts, welds, and joints.
Wood can last in coastal conditions if you choose a dense hardwood like teak, ipe, or shorea. These naturally resist moisture and insects. However, even good hardwoods will silver, check, and develop surface cracks from UV and salt. Softwoods like pine or fir are a poor choice unless pressure-treated and sealed often. In a salty, humid environment, wood generally needs more annual cleaning and oiling or sealing than coated metal.
So for pure durability with the least maintenance in a coastal area, I would rank: 316 stainless or marine-grade aluminum first, then dense hardwoods, then galvanized steel, and finally untreated softwood or standard steel. Also match your hardware — use stainless fasteners. If you love the look of wood, accept that it’s a maintenance commitment; if you want a set-and-forget bench, go with powder-coated marine-grade metal.