Now comes the harder part, we will get the dodge tool again , but this time we will have a very small brush for the highlights of the edges, this will used to create a specular highlight effect that we see so commonly in metal, so you paint it in the areas where there are edges.
After the previous step we will create a selection, in this case the area above the top edge to give it depthness, and don't forget, always feather your selections in order to avoid hard edges
Following that we will do the same we did with placing the lightsource, but this time it will be inside the selection that we have made, so paint it with the dodge tool again NOTE: THE DODGE TOOL ALWAYS HAS THE "HIGHLIGHT" FUNCTION ON, we do the same with the edge in the left.
Now we select the area inside, which wont sufer much editing, and feather it out and give a slight shadow coming from the top, for this we use the BURN TOOL with the same settings as the dodge tool, (highlight mode).
Taking the next step will be doing the exact thing in step 8, except that we will start shadowing the down areas, with the burn tool again.
This next step will be the one where you have to make it really seem that there is a realistic lightsource, so you select again your starting selection of the rectangle, and apply again a filter modifier, but now you'll right click and click on "select inverse" in this way we will be able to paint the exterior without messing around the interior, WE get the burn tool again and we will start painting in under with more itensity and very low itensity on the top, until we get a hard shadow, and try to make the transition between the elevated metal and the texture in the background seem noticable, by painting it with a small brush (maybe 5 pixels) with color burn in the areas that the texture starts.
We are almost done with Part 1!!, now this is where your original part comes, you will pick the dodge or burn tool and mess around till you think you got the desirable effeect, in my texture I darkened a bit the shadow areas, and made the transition between the base and the elevated metal even more noticable ,as well as some random noodling.