I suppose when you are talking about black metallic reflections, your are seeing that while using “Hit Lighting for Reflections” with Hardware Ray Tracing enabled.
Try doing this in your material:
Feel free to tweak that “Fallback” value, especially when dealing with a rougher metallic material it would probably go a bit higher in value (0.5) and make it look a bit darker but not completely black. One could probably go further and remap Roughness to Metallic Fallback and let it change dynamically and accordingly. But that’s for another day …
You will probably end up with very similar looks + proper opacity in reflections + properly rendered Niagara particles in reflections + nicer direct shadows (VSM) in reflections.
Just turn off SSR: ShowFlag.LumenScreenTraces 0
BTW, I think that “Normal” input label is a bit misleading as some may think it has something to do with the normal vector / map. It does not. “Default Material” sounds probably better?