As someone who lives in a region with heavy rainfall, I completely get why this question is on your mind. The short answer is: it depends on the material of your bench. But let me break it down realistically so you can make the best choice for your patio or garden.
If your bench is made of cast aluminum (the most common high-end outdoor furniture material), you have little to worry about. Cast aluminum is naturally rust-resistant because it’s not made of iron or steel. Even if you never cover it through months of rain and snow, it won’t rust. The paint or powder coating might fade or chip over the years, but the frame itself will stay solid. In fact, many cast aluminum benches from good brands are designed to last 20+ years without rust, even in frequent rain—thanks to a galvanized or powder-coated finish that seals out moisture.
If your bench is steel or wrought iron, then yes, leaving it uncovered every winter in a rainy climate will likely cause rust spots to appear. Steel is strong but porous, and rain (especially if mixed with salt from snow-road treatments) will penetrate unprotected surfaces. A quality rust-inhibiting primer and paint can help, but without a cover or yearly repainting, you will see rust within one to three seasons.
If your bench is teak or cedar, rust isn’t the issue—but rot and mold are. These woods are naturally resistant to decay, but prolonged exposure to constant rain without any cover will still cause them to gray, split, or develop mildew. A good sealant or oil once a year can extend their life dramatically.
So here’s my honest take: if you want zero maintenance in a rain-heavy area, choose cast aluminum. It’s the most forgiving material. If you have steel or iron, a waterproof cover (canvas or vinyl with a breathable lining) is a cheap insurance policy—like spending $30 to protect a $300 bench. Even with cast aluminum, a cover keeps the seat cooler in summer and prevents dirt from building up. But no, you don’t have to cover cast aluminum every winter to prevent rust; it simply won’t happen. For other materials, a cover is not optional—it’s essential.
In short: check what your bench is made of. If it’s aluminum, relax. If it’s steel or wood, covering it every winter is one of the best things you can do. Your bench will thank you with many years of comfortable use.