Yeah, well, my Metal Muff is eating up batteries like crazy, and I've decided to screw the batteries and get an adapter. But, before I go out to buy one, I decided to look around the house to see if I had a 9v adapter. Well, I found one, it's a 9v, but the "mA" thing says 600, and on the metal muff guide, it says it accepts 200mA, would the adapter that I found blow it? Or, err... what is mA? I'm not very techy when it comes to stuff like that, haha.

Your Metal Muff draws 200mA. The adapter can handle 600mA, so basically it can handle 3 Metal Muffs. It will work fine. If the voltage is the same, you won't have any problems.