Why Do Some Metals Glow When Heated?

Some metals glow when they're hot because their atoms are moving really fast. When you heat a metal, like a piece of iron or a light bulb filament, the energy makes the atoms vibrate more and more. As they move faster, they start to release light, first as a faint red, then orange, yellow, and finally white when it's super hot. It’s kind of like when you rub your hands together: the harder you rub, the warmer and brighter it feels.