"Phoenix? Sure I've been to Phoenix: quiet place, very peaceful. Loved it. Why, I was there twice last week."
Nikon D90, 50mm lens, f/4.0, 1/800s, ISO 200. Matrix metering here takes the whole enchilada into account for the exposure. That means that the bright window filling most of the frame is accounted for most by the light meter in the camera. Done another way, metered lower with the model (me) taking up more room in the frame the window would be completely white (blown out) but the model would have a more even exposure. Use metering to manipulate the feel of your images.