Drilling through a hard surface necessitates the use of specialist drill bits. Drill bits are not intended to pierce through metal. As a result, they are readily worn away. As a result, strong bits that can drill through metal without being destroyed are required. The most common cause of unable to drill through metal is when the hole you have drilled does not go deep enough. If you stop drilling before the depth is reached, the bit will need to be changed. This could be difficult if the hole is large or deep. If the hole has been drilled too far, the metal may be weakened where it was pierced. This may cause it to break later on when a much greater force is applied. Drilling too far also risks damaging other nearby materials, such as wood or drywall. These materials may be penetrated instead. Some metals, like zinc and copper, are soft and can be drilled with standard drill bits. But these metals are usually used for their appearance rather than for their strength. They are easy to drill because there is no risk of breaking off a bit while drilling. Other metals, like iron, are hard to drill because they won't break or wear away. But they aren't always unusable; special steel alloys are now used which allow iron objects to be drilled using standard drill bits.