For me, jewelry in pierced nipples is the sexiest thing a woman can wear.  
Clit hood piercings are a turn-on too.  
A lot of it is the way these make me imagine the woman is being stimulated.  

I don't see any visual appeal to tongue-studs, but they can be applied in quite pleasing ways.  
I don't care for random metal in other places; it's the specifically sexual aspect that gets to me

They take the best parts of their body and destroy them with metal parts, who wants to suck on on a beautiful nip or clit with a metal stud in it.

I think the look is intriguing...

but I don't think I want any piercings, at this moment. I can't imagine it being any more stimulating then what you guys do already.  
Now on guys - Pierced cxxks & nips are kind of strange to suck on and I don't think I'd want to do that all the time but it's all good. They do make me want to tie the guy down, though.  
Anyways, I lean more towards an appreciation of the natural design....

I do not really care for such things, but they are not a turn off for me, more of an interesting conversation piece.  I have had some interesting conversations about piercings and the placement of them, as to whether it increases sensitivity, orgasm, etc.  Does it turn them on or is it meant to turn the guy on or maybe both.

Also, as a side note, I sometimes date young (over 21 but less than 30) under the radar/non pro ladies and I have noticed than more and more have nipple and/or clit area metal than I have ever seen.  Often these are the "girl next door"  types that one would not automatically stereotype as an intimate piercing type person. No tattoos, no other indications.  

Make me remember the song "Don't you wish your girlfriend was a freak like me

...and really didn't notice during the activities. I don't like nipple piercings. I'm also not a fan of clit or labia piercing but I know a lady that had a small, very feminine one. It looked good and didn't interfer (as far as I was concerned) with the activities. She removed it a few years ago stating she was simply tired of it.

However, I am intrigued by the nut jobs that get extensive facial surgery with implants in order to look like snakes or satan with cleft tongue, vampire teeth, and knobby foreheads. 'Intrigued' along the lines of schadenfreude.

with one of my favorites that her nipple rings were a turn off of my desire to nibble and or suck on her nipples she removed them whenever we had a session. One of the many reasons I came back time and time again and we still are friends.Metal in the belly button don't bother me because belly buttons don't turn me on.

especially on the face.  But nipple piercings are the worst.  I'm always afraid of hurting her if she's got metal in her titties.  Do not like.

I like the individual aspects of piercings and ink. Nothing like barbell nipple piercings.

do not desire hardware for my software

I was in a coffee house in Rotterdam Germany and getting horny thinking about some of the women in there. So I started speaking with an older one who had decent language skills and after a while she suggested we go to her place nearby. We went and when the arrangements for money had been handled, she disrobed. When she got her knickers off she looked like a Christmas tree down there.  She must have had 15 or 16 loops, studs and rings hanging from her pussy lips. Her labia were both extended to nearly 4".  It didn't turn me on though I couldn't stop staring. This she took as if I liked it. I was wondering how I could ask her to put her pants back on.  We finally settled on miss and anal from the rear.  Her tits were nice with no piercing, go figure.  I didn't have much fun as I couldn't stop focusing on the metalic jungle up front. BTW, she gave no signs of her 'freaky' nature up front.