Well, it depends. Your camera flash unit is good for some things. But for landscapes and nature photographs, I find that the natural light is really the best. It’s the way natural light behaves and changes and interacts with our subjets, that really creates the most potential for dramatic photographs. But in situations when you are close to your subject, the internal camera flash unit may give you the light boost you need. Mostly though, I use this flash for taking pictures of people indoors or at night. I haven’t really found much use for them in most of my outdoor, nature work.
You CAN create very wild effects, shooting cars in the city at night, and on freeways, and of crowd shots, with the built-in flash; but for nature photography, I really feel you are better off with natural light, fast film and a good tripod; or an external flash unit which is way more powerful and versatile.