Here's why:

* Metals are excellent conductors of heat. They allow heat to flow through them easily.

* Insulators resist the flow of heat. They are materials that prevent heat from transferring readily.

Therefore, a metal door knob will readily conduct heat, meaning it will easily become the same temperature as the surrounding environment. If it's cold outside, the knob will feel cold to the touch. If it's hot outside, the knob will feel hot.

In contrast, materials like wood, plastic, or rubber are better insulators and would not feel as cold or hot to the touch.