The pictures below were taken on a recent vacation trip to Maine, on a foggy morning. I am not saying these are "good" or "bad" pictures, but they do demonstrate the use of a fill flash to lighten up the immediate foreground.
These first two pictures are obviously before and after shots. The second shot shows the back of the chairs as they looked to the human eye, using the fill flash. But you may like the first shot better because of the greater contrast.
This final picture is an after shot. Unfortunately, against my self-imposed guidelines, I deleted the before shot before I downloaded it from the memory card. So, the before shot is lost forever. That's too bad, as the difference is remarkable. In fact, the flash during the shot below was so short in duration (aren't flash speeds measured in thousandths of a second?) that my eye never saw the light bouncing off the reflector material on the surface of the sign. I only noticed it when I viewed it afterward on the LCD.