Short answer: what you want to do is to switch to spot metering mode, place the face of your subject in the exact center of the frame (no need to zoom in unless the subject's face is really small in the picture), press exposure lock, reframe and take the shot - now the subject will be properly expose and the background will be over-exposed.

Longer explanation:

Metering modes:

• In the "smart" metering mode (Canon calls it evaluative, Nikon calls it matrix) the camera looks at the entire image, apply some magic formula and decides on a setting that work for the entire frame, this is great but if there's something very bright or very dark in the picture it can throw the exposure off since the camera doesn't really know what the impotent area is and what kind of picture you want to take.

• In spot metering mode the camera only looks at a tiny area in the center of the frame and decides exposure based on that, this let you decide what is properly exposed (and let the rest of the picture's exposure falls where it is relative to the area you meter on).

• The other metering modes are not nearly as useful as those two and I suggest not to use them unless you have a specific need.

Exposure compensation is a different but somewhat related concept, after the camera decides what the "right" exposure is based on the metering mode you can override it and tell it the picture should be brighter or darker - this is useful if whatever you are spot metering on is not medium brightness or if you just want to make the picture brighter or darker (just because you think it makes it look better).

And finally, there's manual mode, in manual mode you set the exposure in absolute terms and not relative to the camera's decision - it sounds a little scary at first but usually in difficult lighting it's just simpler to switch to manual mode and set everything yourself (you can usually see the camera's metering when in manual mode - so you can set your initial values based on the camera's meter and then you don't care if something bright or dark suddenly crosses your frame or if your subject is really in the spot metering area or not and if your exposure lock is on or off)