That's an excellent and very practical question! When it comes to heat retention under the sun, metal, wood, and plastic benches perform very differently, and the choice significantly impacts your comfort.
Let's break it down. Metal benches, typically made from aluminum or powder-coated steel, are the fastest to absorb and conduct heat. On a hot, sunny day, a dark-colored metal bench can become too hot to sit on comfortably without a cushion. However, they also cool down the fastest once the sun sets or they are in the shade. Lighter colors and textured finishes can help mitigate heat absorption slightly.
Wood benches, especially thick hardwoods like teak or ipe, have much lower thermal conductivity. The surface warms up gradually and often feels warm but not scorching. The heat is concentrated on the very surface, so the bench remains relatively comfortable. However, darker stained woods will retain more heat than natural, lighter tones.
Plastic or composite benches fall somewhere in the middle. They heat up more than wood but generally less than bare metal. The material can sometimes feel uncomfortably warm and may even retain heat for a while. High-quality composites often do better than basic plastic.
So, for heat performance? Wood is generally the most comfortable in direct sun, followed by high-quality plastic/composite, with bare metal being the hottest. But remember, metal wins for quick cooling and unmatched durability. For a metal bench you can use anytime, consider placing it in a shaded area or using removable outdoor cushions for the hottest parts of the day.