This works for paints, plastics, metals and other types of materials where you have a base color or texture and some reflection on top of that. Here’s how it is done in Koru:
You see that the layer has both diffuse and specular blocks enabled. Diffuse block defines the base orange color of the material, while the specular block controls the reflection. You can read more about the layer parameters here, but the most important parameter here is N - the index of refraction, that controls how much light will be reflected (and refracted) by that layer. Set it to 1 to avoid reflection and refraction, use higher values to get reflection.
Here is the same material with N = 3:
You see that our material becomes much more reflective. To make a metallic reflection, you need to switch IOR selector to “Complex” and increase the value of K parameters which controls the metallic reflection:
It now looks like a painted metal. Further increasing of both N and K values gives you a very reflective metallic material:
You can add another layer to make another reflective layer on top of this one. Add a layer and enable specular block there. Make sure the layer is added above the current one:
Here we set that new layer to have specular block only, then we configured it to be orange and to have N of 1.5, so only edges are reflective. This second layer adds another orange reflection on top of the main metallic one. Have a look at lacquered alluminium materials in Koru materials library to see more examples of this effect.