Here we are going to learn how to create some nice looking screws to add to your metallic interfaces. First we need something to put our screws into! Make a rectangular linear gradient with colors gray and gray, making sure that the lighter of the two colors is towards the top.

Use your ellipse tool to create a small inlay for our screw. make sure that the darker of the two grays is towards the top.

Now we are going to create our screw head. Make another smaller circle within the circle inlay we just created. Change your gradient mode to Radial.

Position your gradient so that the lighter of the two grays is in the center, creating a spherical effect.

Now we are going to add the rivets of the screw head. Create a rectangular gradient similar to the one below. Change the gradient mode back to linear, and position the gradient so that the darker of the two grays is towards the left.

Duplicate this rectangle and rotate it to create the second rivet. Your screw is complete, you can now duplicate your screw by selecting all of the parts, while holding shift, and copying/pasting them by pressing Ctrl+C and then Ctrl+V.

Next I added a metallic texture to my background. This can be done by creating a new rectangle above your original gradient, but below your screws. Instead of filling it with a gradient, choose "pattern" from the Dropdown menu and select a metallic texture that suits your image. Next change the layer mode to "overlay."

Your finished! Here is how my interface turned out.