Starting to be overused in web design/graphic design, brushed metal is a gray texture with thin horizontal or vertical hills and valleys running through it. The default theme of Enlightenment DR16 is based on a brushed metal texture.

To make brushed metal in Photoshop (and GIMP too):

• Render black and white clouds
  
• Lower the contrast and increase the brightness slightly
  
• Make a new layer filled with white and layer options set to multiply
  
• Use the add noise filter on the new layer, 55 or so works well in Photoshop
  
• Motion blur the new layer in the desired direction
  
• Adjust brightness/contrast of the background layer to fit your tastes
  

You can also do other things like colorizing and adding rust to the metal