First, create a new image, and fill the background with the color that you like.
Use Rounded Rectangle Tool to draw a shape that you want your button to look like.
Now is the time to add Inner Shadow to your shape. Right click on the shape layer and select Blending Options...
Layer Style window will open, select the settings that you see on the screenshot.
In the Layer Style window select Inner Glow on the left and use settings that you see on the screenshot.
In the Layer Style window select Gradient Overlay on the left and use settings that you see on the screenshot.
In the Layer Style window select Stroke on the left and use settings that you see on the screenshot.
Press ok when you done and your image should look like mine.
Congratulations, now you know how to create metal buttons in Photoshop.
