For my own remodel, I chose stainless appliances, orb hardware and light/faucet fixtures. I think it is just a matter of personal opinion, as there is no written rule (that I know of).

For me it depends if I'm going for a solid/monomaterialist look, or if I want the interest (or chaos depending on your preference) of varied different materials.

My last kitchen was black appliances with deep ORB (looked black) hardware. My sink and faucet were SS. Lights were a patina brown with parchment glass. I don't know if I consciously tried to match these elements to the other items they were nearest, or if it was coincidence, but now that I think about it - ORB/blackened hardware was probably inspired by the appliances. Ee originally had the house built with cream porcelain, thinking we'd have almond appliances, but chose black at the last minute and forgot to change the hardware... it looked horrible until we changed to the blackened ones.

The brown/parchment lights were over 1) the island (Earthen Terra Formica) and 2) the table & windows (table is a deep coffee color, windows were dressed with parchment voile sheers and loden panels, tied back with help straps I made).

The faucet was selected because I wanted it the same as the sink.

I am building a new house now, and will have ORB or patina(ed) iron hardware. So far my lighting choices (struggling to pick) all have metal that's in the brown family. Sink will either be SS or Silgranit in Biscuit (learning toward this). Appliances will be SS. I will probably do the faucet in brushed SS, but I'm not sure on this one. Haven't thought much about it yet.

To me, SS appliances read like a neutral. I just don't see them for very long when I go into a kitchen, unlike white, almond, black or even the metal-finish ones like the Jenn-Air ORB or whoever's blackened steel.

So for rules, I'm not sure there are any. Pay attention to these elements in photos, friends' kitchens, etc. and the only rule seems to be "don't do everything the exact same". Must people have a hodge podge of metal & appliance finishes.

I plan on doing forged iron hardware, stainless appliances and brushed nickel faucets. The light fixtures are mostly black or very dark blackish ORB.

I chose SS appliances, ORB hardware, ORB faucet and lighting at our lakehome. Orginial owner had SS hardware with the ORB faucet and lighting and I changed the hardware only because I don't care for SS knobs on cherry cabinets.
Here at home I have SS appliances, brushed nickel faucet and lighting, and black hardware with cherry cabinets.

It's definitely up to your taste. Before I even owned a home, it always bothered me when metals didn't match..... hardware, faucets, lighting fixtures. It still bothers me today. I walked thru an open house this weekend and there were three different finishes for their light fixtures, visible at the same time. This drives me crazy! :) Do you care?

My new kitchen will have ORB hardware, ORB lighting, ORB faucet (with anthracite/black silgranit sink.) ...... and SS appliances. I don't think the hardware needs to match the appliances. I do think the hardware should definitely match the lighting... it should probably match the faucet too.... and then the faucet should match the sink! (a SS sink and ORB faucet are bad to me.) Again, this is just my taste here.... (but you asked!)

I just went with what I liked, and ended up with stainless appliances, sink and faucet; dark (almost black) ORB lighting (pendants, 3 & 5 lite fixtures and semi-flushmount) and antiqued nickel pulls. The counter tops are a dark gray with brown/black flecks. It sounds like quite a mish mash of color, but it seems to work in my kitchen - sort of a gradual variation from silver to black...

HTH,
Dawn

Also - think about what color your counter top will be. I have stainless appliances and picked all ORB for the hardware, lights and faucet. I changed to a SS faucet though b/c my counters are dark black & brown & I thought my faucet would blend in too much. I wanted it to be noticed since I spent so much time picking it out! I don't think it matters that my faucet is a different finish from my hardware & lights.