..the material of the gloves will affect 'material' of punches?

>..the material of the gloves will affect 'material' of
>punches?

No. Wearing iron gauntlets (for example) will not exploit a vulnerability to iron.

I've seen various items around such as brass knuckles - do these influence damage at all? Apart from dam/hit roll of course.

Brass knuckles have another affect other than the immediate +hit/dam. Some experimentation and paying close attention to your skills may clue you in.

There is a pill you can eat that will give your punches a magical touch.

Said item does change your "punch" singular, to a magical attack. Originally it would work with all but many years ago Zulg changed it to only one attack per round as per the help file.