easy rendering for Rhino in Windows
I had the same problem when i started, i believe it's because the metal is too shiny and it's a perfect mirror. so it reflects back the Hdri perfectly, while the other material doesn't.
Your HDRi image might be too small, you can get around this by getting bigger HDRi's or by making your model bigger.
Here are a few sites with bigger hdri's
Here are some Huge Hdri made from zbyg expaned to be XL (I use these ones mainly)
Hope this helps
The larger HDRIs are a good solution.
Turning down the sharpness of the reflection a little will also solve the problem.
thanks for your answer.
I tried high res image but it didn't work, so I reduced sharpness of the reflection and it gives good result, so that ok!
I found that sharpness values of 0.99 work for this. What value of sharpness did you decide to use?
I tried 0.9, that was good but you're right because with 0.99, it's better.