There isn't one single instrument that measures "metal" in the way we think of it (like a type of material). Instead, we use different instruments to measure various properties of metals, such as:

* Thickness: Calipers, micrometers, and thickness gauges

* Weight: Scales, balances, and load cells

* Hardness: Rockwell, Brinell, and Vickers hardness testers

* Tensile Strength: Universal testing machines

* Composition: Spectrometers (e.g., XRF, ICP-OES, ICP-MS)

* Temperature: Thermocouples, pyrometers

* Electrical conductivity: Conductivity meters

* Magnetic properties: Magnetometers

So, the instrument you need depends on what specific property of the metal you want to measure.