Hi Alex,
     A metal tutorial? Actually I have described my take on painting
   metallics several times here on minipainter.

   Furthermore, here is some thoughts on how to paint metal or steel:

   The metal is given a basecoat of Boltgun Metal and shaded with
   thinned down Chaos Black. Then I work up highlights from Boltgun
   Metal over Chainmail finishing with Mithrill. Now the area is subtly
   glaze down using a mix of purple and dark green ink thinned with
   water and followed by touching up the final highlights with Mithrill
   Silver. It is just a question of working back and forth - from light
   to dark and back again - until it looks right.
   Do not be afraid to go bold in the contrasts, just as long as
   you remember to glaze and re-highlight.

   Finally, you could try making a search on "Tamiya" here on
   minipainter to see how Tamiya clear colours can be used to glaze and
   thus enhance already painted metal areas. I think they work wonders!