Depends on the lock, but mostly metal and iron.
It depends what material they are made from
The keys used to be made out of ivory but are sometimes now made out of plastic like material over wood.
Rosewood.
The keys of the clarinet can either be made from nickel or silver.
Chrome Vanadium Steel is the most common material used.
Keys can be made of almost any solid material. Most modern keys are made of brass, aluminum, or various alloys that are of similar durability yet softness. The keys for old mortise door locks were made of iron. Many locks made in the middle ages and earlier used keys made of wood.
Old skeleton keys were typically made of iron or brass. Iron keys tend to be older and have a rustic appearance, whereas brass keys were more common in the 19th and 20th centuries due to their durability and resistance to corrosion.
Ebony, a heavy dark wood. The advantage of ebony (and ivory for the white keys) is that these natural materials do not get wet from perspirationand become slick.
Keys are usually made from some metal or alloy. If they are, they are good conductors, both of heat and of electricity.
The main difference between a marimba and a xylophone is the material used to make the keys. Marimba keys are typically made of wood, while xylophone keys are made of metal or synthetic materials. Additionally, marimbas are larger and have a deeper, richer sound compared to xylophones.
Brass , is the most widely used metal for keys.
When buying piano keys, consider factors such as the material of the keys, the weight and responsiveness of the keys, the size and spacing of the keys, and the overall feel and comfort of playing on the keys.