When I discovered metering modes, it made a huge difference in how I take photos, and the quality of them.
Metering is where you tell the camera which part of the frame it should consider when it decides what kind of exposure it should make.
If I'm taking a photo of a little insect on a flower, I use spot metering and I make sure the auto focus point is pointing exactly at the insect. Then the photo is perfectly exposed for the primary subject (the insect.)
I do the same if I'm taking a photo of a daylily in bright light. I make sure the daylily is the auto-focus point, and using spot metering I get a perfectly exposed daylily photo.
The default on the camera is usually a "center weighted average" where it tries to figure out an average exposure based on everything in the center of your photo. That's fine for most photos but it's not to have really fine control over the exposure in situations like this.
