You're used to using flash when there's not enough light—such as indoors.
You can also use your flash when photographing in the sun for the same reason—when there's not enough light.
Question: When is there not enough light in the sun?
Answer: The shadows
In the top photograph of the pumpkin, no flash was used.
You can tell because the shadow is dark, and there's no tell-tale hotspot from the flash.
What wrong with the photograph?
The pumpkin doesn't look very orange, because it's in shadow.
And, the sky and the porch railing are washed out.
The bottom photograph was made with flash.
The flash has brightened the shadow, and allowed the sky and railing to be darker.
The hotspot from the flash isn't pleasing.
A reflector would have brightened the shadow without the hotspot, but how often do you have someone who can hold a reflector for you?
Use your flash when photographing in the sun and there are shadows.
For example, use your flash when photographing . . .
1) Someone wearing a hat with a brim that is casting a shadow on his or her face.
2) Someone with sunlight on one side of his or her face.
3) A still life, such as a 1940s Bakelite radio at an outdoor flea market.
4) A valley that's half in shadow from a mountain, and half in the sun.
No, unfortunately, you can't do #4.
That's because the flash on your camera will only reach about ten or so feet.
So, if your subject is farther away than about ten feet, fill flash will not be useful.
When using fill flash, the color of the light produced by a flash often appears to be too blue.
If so, try the flash white balance setting.
Or, filter the flash with a warming filter.
Go to Flash Filters.