Just a little while ago, I got a chance to paint up a dreadnought for the Grey Knights.
Doing a mini in that much metal can be tricky- especially something like a dreadnought that needs to have two different types of silver to distinguish the machine workings from the armor. Even when you can make the silvers distinct, there are other troubles.
Often, when you're using that much silver it tends to neutral out the mini a little too much. To combat this, I created a bright lava base so that I could have a light source interacting with the rest of the miniature.
Altogether, I think this approach worked out rather well.