system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do things like metal and lava turn red when they are are hot?
gpt
It is  thermal radiation. The thermal radiation that everything emits depending on temperature.

Glowing orange red is the lowest temperature that emit visible light. The hotter it gets the whiter it gets and even hotter it will look blue.

The light from a incandescent light bulb and the sun is black-body radiation but it is whiter at the temperature is hotter.

Thermal radiation it emitted at all temperatures but it has to be over approximate 798 K (525˚ C, 977˚ F)  to be visible. At lower temperature it is only infrared light and not visible.

The heat you feel radiate from hot object at lower temperature is thermal radiation but in infrared. But with special camera often called Forward looking infrared (FLIR) in militery application you can see the thermal radiation  from a human.