What camera and which flash are you using? Are you using it in manual?
Without knowing what camera or flash you are using, its pretty difficult to help.
That is pretty important info isn't it? My camera is sitting here right next to me, don't you guys see it?
It is a 5Dm2 and a 580EX II flash. I only use it in manual because the settings seem to be way off it left in automatic. I do shoot 90% in manual, so it isn't much of a problem besides just guessing, but the camera tries to set the exposure as if there is no flash when in auto. Let's say that it will want to set it for 0.3" and f/2.8 at ISO100, where with the flash, I can set it for 1/100 and f/7.1 at ISO100. The thing I learned last night was that I can leave it at 0.3" but set it to f/7.1 and the color temperature of the photo looks a lot better.
The camera does seem to take good pictures with the proper exposure for whatever settings I use that are close to what they should be.
@Caps18 the simplest explanation for your troubles and inconsistent results may be that you don't have the flash set to ETTL mode. All the comments from others are correct... when using flash, the exposure is a combination of the ambient exposure (as if you had no flash) and the flash exposure. Think of it like two separate exposures superimposed on each other.
The camera's light meter is only telling you about ambient exposure. As @nightbreath said, if you set your aperture/shutter/ISO to give you a -2 exposure then the ambient exposure will be fairly dark. In ETTL mode the flash power will be set by the camera to add enough light to get a correct exposure. In this case, most of the light contributing to the final exposure is from the flash and your white balance will be good (if you set it to flash).
Conversely, if you wanted more exposure from the ambient light, you might increase your exposure, by choosing a longer shutter speed for example. The camera will decrease the flash power a bit (I believe) to still give a correct exposure. In this case though, the white balance might be a bit complex. If there are tungsten lights, you will see more of the yellow color cast. This sometimes looks good for example in the photo nightbreath posted. In other cases, if there are fluorescent lights in the room, you might not like the green color cast.