Depends on what kind of key.
Brass , is the most widely used metal for keys.
A reed, brass (or metal), and plastic for the keys.
Keys are made up of various sorts of metal.
Metal
An instrument that has 15 metal keys is called a nyunga nyunga. These 15 keys are arranged in 2 different rows and is a type of mbira instrument.
Typewriters are typically made of various materials including metal (such as steel and aluminum), plastic, rubber, and glass. The body of a typewriter is often made of metal for durability, while plastic parts are used for components like keys and covers. Rubber is used for the platen and other parts that need to provide friction or cushioning. Glass may be used for the keys or typebars.
Manipulative keys are special keys used to manipulate data in the document.
a regular flute has covered metal keys, and some have metal keys with holes in them. indian flutes are made of bamboo and have no keys, only holes
Many percussion keyboards have metal keys. Some of them are glockenspiel, xylophone and vibraphones. Piano is not a percussion keyboard as it has a string mechanism as well.
The xylophone has metal keys that you strike with a wooden hammer.
In theory, yes. In reality it depends on the distance between detector and keys. You'd pprobably need to get within a foot or so vertical distance between detector head and keys to get a signal.
Tabular Keys are used becasue they combine both Branching Keys and Multi-Access Keys