Hi... So when I'm driving for awhile and begin to brake, from around 20mph and down an odd noise starts in the front right side of the car... It's like metal on metal, and only seems to happen in the last bit of braking or under moderate to severe braking. I have uploaded a crappy recording here:

https://soundcloud.com/cekren/audi-a4-brake-noise

it's a lot louder than the recording picks up, but it was the best I could get with my cell phone...

I know a bit more about electrical than mechanical, so does anybody have any idea what this noise might be? A bad pad/rotor?

 

Check to see if your pads are worn down too much. Check your rotors to make sure they aren't warped and have enough meat left on the bone also.

Also check to see if that circular piece of metal that is behind the rotor isn't touching the rotor itself. I think its like a guard or something but sometimes when taking off the wheel and putting it back on, it can rub against it and push it toward the rotor so every time the rotor spins, it would hit that piece of metal and create that noise. I had that issue before but you know that's the problem when you hear the noise will driving, and not only breaking. Also, if your pads are not worn down, check to make sure the retaining clips are engaged and in the right position. If they aren't it will cause the pads to rattle while you drive.

 

You don't say how long it's been since a brake job, but that sure sounds like pad metal on rotor.