The camera determines the need for flash when shooting in the automatic modes. Even though it's a sunny day the camera may determine a need for fill flash or more light in macro mode. Try shooting in one of the creative modes, start with P - it's the same as automatic but it won't fire the flash. For more control move to Av (Aperture priority) to control depth of field or Tv (Shutter priority) to control time ie... stop action.

If you want to move out of the auto modes completely pick up a book on exposure, there's plenty to choose from. I recommend 'Understanding Exposure' by Bryan Peterson from Amphoto Books.

Ed