Before we discuss whether metal bird feeders can burn birds' feet, we need to understand some basic physics. Metal is a good conductor of heat, which means it absorbs and releases heat quickly. Therefore, if a metal object is exposed to the sun, its surface temperature may rise quickly, and may even reach a level high enough to burn the creature.
However, for birds, their feet have thicker skin covered with a layer of cuticle, which makes them resistant to high temperatures to a certain extent. In addition, birds do not usually stay in one place for a long time, especially in hot weather. Therefore, under normal circumstances, metal bird feeders are unlikely to burn birds' feet.
However, this does not mean that we can ignore this problem. In extremely hot weather, or if the birds cannot leave the feeder for some reason (for example, if they are trapped or sick), then metal feeders do have the potential to cause harm to them. Therefore, if you use a metal bird feeder, you should try to avoid leaving it exposed to the sun in extremely hot weather. You may also want to consider adding some insulation to your feeder, or choosing a non-metal feeder.
Overall, while metal bird feeders are unlikely to burn a bird's feet under normal circumstances, there are still some precautions we need to take to ensure the safety and comfort of our birds.