Answer:
The metal molecules inside start to vibrate faster, causing the solid to change to liquid if exposed to the intense temperature over a long period of time.
Step-by-step explanation:
As my answer states, but for an explanation, lets say you are boiling an ice cube, it will start to turn into liquid water, that is because it has been exposed to that heat for a long period of time. The same will happen for the metal, if its exposed for long enough, it will turn into a liquid, then can be turned into a gas because the molecules are vibrating so quickly that they start to easily move apart.
Hope this helps, let me know if any more clarification is needed.