The mini above and the ariticle on cool-mini are excellent regarding what is known as
NMM (non-metallic metal) are very impressive wonderful techniques.
Barring that, you can actually paint chrome - but it is NOT easy to work with.
My necrons are painted in a chrome based color scheme, and I have to say, it has been quite the struggle to make it work.
The paint;
Allclad II Chrome paint.
http://alclad2.com/finishes/high-shine/alc-107-chrome-for-plastic/
This is amazing stuff. Its airbrush only, and requires two layers of their very glossy black primer as an undercoat, with quite a bit of drying time underneath. It is a lacquer based paint.
The results are stunning.
It is used a lot my scale modelers for cars and airplanes.
The challenges
Priming
you must use the proper primers, and they must be used according to the manufacturing instructions...no short cuts.
(primer, wait one hour. Primer second coat, wait 24 hours, then paint on metallic paint).
Working with the paint
As this paint is highly reflective, anything you paint over it (wash, other layers, etc.) detracts significantly from the affect.
You can use some of the all clad transparents to a degree (I think they are actually laquer dyes, not actual paints) but putting other coats or colors on the model is challenging.
Doing touch ups is also a great challenge, as painted on is no where near the affect of airbrushed on.
How to work with it
I have found that I can do vehicle base colors, or shading with it (I have done a lot of metallic vehicle body paint commissions, including a thunderhawk) and that if used as a zenith highlight on infantry, it can work.
But overall, this stuff is expensive, and has quite the learning curve.
Alternatives
Supposedly there is an even better chrome paint, Spaz Stix Chrome - but I have never worked with it.
If you are already a good painter, I might suggest trying to use the
NMM methods....the chrome paints can work, and work better for some applications - so they might work for you, but expect them to be a bit tricky.
Best of luck.