Producing weathered wrought iron

ok assuming the wrought iron was originally black (which it is around here), there are several levels of weathering.

new = flat black paint with a hint of light grey or white added

been outside for a bit = "new paint above" with a very faint light grey wash for your average wrought iron finish

add a light dry brushing of white and then rust to create a neglected look.

when drybrushing I would concentrate the white on detail areas as these would fade faster (dunno why, there is a wrought iron place near my house and the stuff they put out front always has whiter detail) also a light white wash that was allowed to settle in the detail would do good... faint drybrushing of white over the rest... pick out some rust with a tiny brush...

that should do it!

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if it is not black I would start with a dark aluminum with a diluted dark wash on the detail and go from there like above...

Dana,

I'm not sure that I would go with metallics as most wrought iron I've seen is flat black. It seems to go from a very deep flat black to a very , very dark gray with rust spots here and there. (at least that's what the wrought iron on both my neighbors and my front porches look like. Before we repainted them). I would airbrush a base coat of the darkest black I could find and then drybrush several overall layers of lighter blacks/dark grays over it, finishing with areas of rust.