Using the procedural Scratches texture is a great way to add weathering and wear to materials, and to metal materials in particular. These are the settings available for the Scratches procedural.

Set the color of the scratches. In cases where the texture is used for opacity maps set this to black.

The color between the scratches.

Use this to set the overall scale of the scratch pattern generated.

Bump Height
Increase this value to obtain deeper scratches. It can also be set to a negative value to obtain very subtle scratches.

Use this to control the number of scratches generated.

Use this to set the size of the individual scratches. Expand to control the scratch thinness (width) and falloff (fade).

Directional Noise
This controls the randomness of the direction of the scratches. Decrease this value to have scratches in a more aligned direction. Expand to choose Direction Field mapping.

Controls the straightness of the scratches. Increase the value to have more irregular scratches. Expand to access the Noise Scale slider.

Controls the number of unique scratches that are generated. Expand to access the level scale.

In this example a layer of paint have been applied (as a label) on a metal material. The Scratches texture is applied as an opacity map on the label revealing the metal under the paint.