These crystals are attracted to each other, and this attraction bonds them together in a matrix or grid. However, when you heat up a metal, the crystals vibrate faster and faster until the bonds weaken. The metal then becomes malleable, and may even melt into a liquid if the temperature is high enough. Because of the flexibility of the bonds, metals are ductile, which means they can stretch and move to a limit without breaking; the process of hot-working mentioned above makes sure this characteristic is retained.
