So maybe it means that Iwaki likes Visual Kei bands like X-Japan (sort of glam metal style music with a heavy edge, and the musicians wear elaborate makeup, costumes, and hairstyles), or maybe just X-Japan in particular? (X-Japan has a heavy metal sound, combined with a bit of classical style, due to the fact that drummer and main songwriter Yoshiki is also a classically trained pianist--their ballads often have elaborate keyboard and string arrangements.) Or maybe it's nothing more complex than Iwaki thought that "Rusty Nail" would make a cool name for his club? Or do the lyrics have some significance for him? You can find the romanized Japanese lyrics here, and an English translation here. Here's an excerpt:

No matter how many tears I shed, in a piece of my memories
Cutoff memories accumulate in my unchanging dreams
Oh-Rusty Nail

I probably won't be able to forget about you
Just tell me my life
No matter how far I try to walk
I won't be able to see tomorrow through my tears

The singer seems to be mourning a lover who has left him, and he may be in the process of committing suicide, judging by these verses:

When you live your life honestly
Then the night reflected in your eyes, certainly leaves behind only shining dreams
Forgetting the loneliness that greets the morning
I held my red wrists and cried
Let the night end

Shaking, with the door of my memories closed
Cutoff memories accumulate in my blue lips
Oh-Rusty Nail

Of course I don't see Iwaki as the suicidal type, but maybe he named his club after this song because he was secretly mourning the loss of Takaaki, even though he was the one who left Takaaki?

Or maybe I'm making this all too complicated, and Nitta-sensei just happened to like the song. ^_^