Honestly, yes—most bare metal outdoor benches get too cold to sit on comfortably in winter unless you are only stopping for a minute or two. Metal is highly conductive, so it pulls heat out of your body much faster than wood or plastic. When temperatures drop near or below freezing, the surface can feel icy almost immediately, even through jeans.
A few factors can change this. If the bench sits in direct winter sunlight, it may feel slightly less brutal, but metal still loses heat quickly once you sit down. Wind, shade, and damp air make it worse. A thick coat and insulated pants help, but they are often not enough for a long sit because your weight compresses the fabric and reduces its insulating power.
If you want to keep using your metal outdoor bench in cold weather, a weather-resistant outdoor cushion is the easiest fix. You can also drape a folded blanket over the seat, add a wooden seat pad, or move the bench to a sheltered, sunny spot. So the practical answer is: without a cushion, a metal outdoor bench is usually too cold for casual winter sitting, but with one it can be perfectly usable.