How to get realistic dirt on metal? I'm trying to create a stainless steel metal with dust on it. There' something I'm not understanding. I'm using a sun lamp in my scene and the effect is pretty weak:



Hoewever, if, under viewport shading, I uncheck "Scene Lights" and "Scene World", I get this - which is much closer to what I'm going for (although still not great):



The problem is that I want to use the sun lamp and not an HDRI. Basically, I'm looking for a good way to add dirt to a vehicle in a scene lit with a sun lamp.

So one question is, why does the second image look so much better? How do I get the first image to look more like the second?

More importantly though, how can I get some realistic dirt and dust on a metal vehicle?

Thanks for any help!
Thanks for the responses everyone. I realize I was asking several things at once. Here's what I figured out:


The sun lamp was too dim. That's why the results were not comparable with the HDRI.
I had to really turn up the the "Strength" and "Distance" settings on the bump node to get some effect. And turning down the roughness setting allows the "Dirt" to look like it's sitting on top of the metal.


Unfortunately, the effect looks more like metal than dirt, but the questions I was asking in this thread are answered.



Edit: I found that inverting the Bump node, gave more of the look I was going for: