How do you clean metal hardware of leather pieces?

[AteRiri]

How do you take off rust/discolouration from metal (near leather - like leather jackets, bags?

I use the same product as I used to use on my horses' tack: www.lincoln-equestrian.com/3786.html Just apply with a toothbrush if large enough, otherwise a cotton bud.

I figured if it worked on thousands of pounds worth of saddle then it'll work on my 10x cheaper handbags and it does do the job.