I opened up my 360 and this thing fell out...I'm not sure where it goes or what it is or even what it does.

Is it necessary that I put this back in my system? I assume it was there for a reason

It's just one of the small grounding strips that's on the side of the DVD drive, there's another one on the other side of it as well. It's perfectly fine to leave it out of there, it's not going to cause any harm or good either way.

Those pieces sit on the metal chassis, they support the sides of the dvd drive.I'm not sure if they're really needed, I think they just provide a bit of shock protection.

EDIT: You posted just a few seconds before me, oh well

That goes on the part where the dvd drive hits the metal case (by the front panel).

I think it's there just to make sure the dvd drive is not loose and cause vibration problems, I'm sure you're ok with it off but I'd put it back on if your case is still open.

Thanks for the help guys. I thought it came out when i was removing or putting the DVD-Drive back in, but I wasn't sure.