For its time, there was a lot of science to that science fiction. It still plays well today, and it's in color, so there's no reason not to watch it.
Anyway, when the monster was pursuing them, they took shelter behind "Krell metal", supposedly a very superior kind of steel. But the monster wasn't stopped by that; it could draw on all the power of the planet, to heat the metal, first red hot, and eventually white hot, and softer than putty.
If you have light bulbs in your house, you may see labels on them, referring to "color temperature". The higher the temperature, the brighter the light.
Measured in Kelvins I think, which makes about as much sense to me as measuring wind speeds in suction power or something.