In the 'old days' meters were center weighted, usually with a bit of a emphasis on the lower 2/3rds of the frame to avoid the sky contributing too much. Lots of things fooled such a meter - like backlighting, or a white or black main subjects. In modern times we now have the multisegment meters that make use of a large array of examples to compare the scene too in an attempt to overcome these kinds of challenges. The very latest meters from Nikon and Canon now use color as well.
All that is good, and helps the beginner get properly exposed images in a lot of situations without having to understand metering and exposure. For those of us who do understand such things, it becomes almost counterproductive. The multi-segment metering is invisible in its operation, and slight differences in framing can change the exposure dramatically. So - many resort to manual metering, or simply manual exposure. If you do use the meter for manual exposure I think you are better to switch to a more predictable metering pattern - either the center weighted or spot meter modes. The spot meter is the best, in my opinion, as it uses only the center of the lens and it is pretty easy to fill the meter area with a patch of solid color.
I've been using spot mode on my 7D lately, and find I'm getting more consistent exposures. Even with flash, I'm using the flash exposure lock (I have the mFn button mapped to F-El) to meter first, then concentrate on composition. Here is an example of a shot with bounce flash - but spot metering...
3 hours ago