Metallics and pearls demand a very good gun technique. If really affects the appearance of a metallic if you spray it slightly "dry" or "wet". If you spray a metallic BC/CC, it is a little more forgiving getting the color and evenness of the shade right, without having to worry as much about orange peel, or runs, or sags. Not that you do not have to worry about it, but not as much. Once the color is right, just shoot the clear on it, to get the gloss.
I have seen a few cars painted with a SS metallic, and sprayed slightly "wet" and look really good right after spraying, and then when looked at again slightly later, a very slight "sag" in the paint, that becomes very obvious because the metallic highlights the sag.