Strange pixelation and noise

[PB81]

I rendered this with a custom lighting environment downloaded from the keyshot library. The materials I used include anodized polished aluminum, chrome polish (on the rings which show the most noise), and matte white for most everything else. Is this an issue with the model? I wonder because if I do a simple matte white material on the whole thing, it doesn't show the artifacts/noise.... it's only when I apply the metalic materials that things get whacky. Is this normal? Is there a setting I'm not doing correctly? Attaching the rendering and then a version with only matte materials, and finally a matte version with simple white lighting.

[DMerz III]

Is there a bump height on those parts? Sometimes if you pull a material that someone else built on a completely different model, the bump height can be too extreme, if you turn that down and it isn't the solve, we might need some more info about your scene, what lighting mode are you using, etc?

[Esben Oxholm]

Hi!
Looks a bit like caustic noise to me. Try disabling caustics (if it's enabled) under the lighting tab in the project panel.

Take a look at this tutorial at 4.30. Not directly related, but might help if this is new info to you
Hope it helps!

https://youtu.be/K0jHnoXhtis?t=270