In this tutorial,I'm going to teach you that how to render an "I-Phone" via 3ds max and mental-ray.First of all download the 3d model by this link...
http://3dexport.com/3dmodel-iphone-4-52392.htm
Then import it to 3ds max and to make "mental-ray" as the render follow these steps.Rendering>Render setup>Common tab>Assign Render(sub-menu)>Hit the first "..." button and select "mental-ray" from the list.
Open up the material editor by pressing "M" key.Then press standard button and select arch and design material preset from the "mental-ray" sub list.
After doing that change settings to these numbers.Make sure that you've changed main color to Wight.Then apply it to the phone.Make another arch and design material with black color and Reflectivity is "1.0".When you are finished add it to necessary places.So your model should look like this.