Why cameras can get it wrong
Have you ever taken a picture of something you can see is bright - but it comes out looking darker than it should be? All cameras will set the wrong exposure from time to time - no matter how much it cost.
Wrong exposure happens because your camera can't think for itself so manufacturers use a set of guidelines that are great for average light and conditions - but move away from average and there's a good chance it'll get the exposure wrong.
Here's a simple exercise for you to do for yourself which will help you recognise in advance when your camera might get it wrong and you'll need to step in and use exposure compensation or make a fully manual exposure yourself.
A camera can only do what someone tells it to do and in certain extreme conditions the light meter will be confused because they think the world is grey. So when confronted with something which isn't grey they will set an exposure which makes it grey.
This is why grey cards were created to help photographers get their exposures accurate.
Despite having been using Lightroom for some years 7 Steps to Perfect Pictures has helped a lot with regards to the use of brushes, which I had avoided... and was also helpful concerning the settings/parts of Lightroom that I don't use because I didn't see any difference using them - same as Mike!