Yes, urban outdoor furniture can be left outside all year round without being ruined—but only if it is designed for it and given a little care. The city is a tough environment: rain, UV, freeze-thaw cycles, pollution, bird droppings, road salt, and constant foot traffic all test the finish. A cheap untreated wooden bench or a steel chair with exposed welds may look tired after one winter. Commercial-grade aluminum, stainless steel, HPL, teak, and high-quality synthetic rattan are much more likely to handle year-round exposure.
Material matters most. Powder-coated aluminum is a strong choice because it will not rust, provided the coating stays intact. Stainless steel can also work well, but it needs regular cleaning in salty or polluted areas. Teak and other dense woods can stay outside, though they may silver with age and need occasional oiling if you want to keep the original color. Good synthetic rattan resists rain and UV, while cheap resin can become brittle or fade. Mild steel and untreated softwood are the ones I would not leave out indefinitely.
Cushions and fabric are a different story. Even outdoor-rated fabrics last longer if you store them during heavy rain, snow, or long periods of disuse. Standing water is the real enemy, so choose furniture with drainage holes, raised feet, and frames that let water run off. Breathable covers are better than tight plastic tarps, which can trap moisture and cause mold.
A simple routine makes a big difference: rinse off dirt and bird droppings, check joints and welds, clear drainage channels, and cover or move pieces during the worst winter weather. In snowy or coastal cities, clean off salt and grit before it sits on the surface. If you buy well-made, commercial-grade furniture and look after it, leaving it outside all year is realistic. If you buy delicate decorative pieces and ignore them, the city weather will win.