My 1st attempt at a portrait.

[Nautifish]

I guess these would be classed as portraits...Which is a 1st for me.

 

[lightning_jack]

#1 - flat light, Portrait with cap?? Unmotivated look into the far nothingness of nothing, clothing that is extremely boring
#2 - better - but: where is he looking?, looks like he's "leaving" the pic
#3 - Has some nice sphere, seems like he's coming into the pic (remember: Most of us are used to reading from left to right), still no "portrait" but more a "some guy having a good time at something" where the "something" still seems more important than the subject himself. Maybe that's because of the half of him being cropped.
#4 - snapshot, out of focus, shallow contrast

 

[KmH]

You need to get light up under the caps by using a reflector, or supplimental lighting. #2 is not as bad as #1. The next time you post multiple photos, please put a blank line between them, and number them.

In the last one, the subject is squinting, and has 'racoon eyes' because he is in direct sunlight, a big no-no for doing outdoor portraiture. Dappled sunlight is another lighting nightmare to be sure and avoid. Both can be mitigated somewhat by using supplimental lighting, but the squinting problem would remain.

The best outdoor portraiture is made with the subject in open shade, or diffused direct sunlight, and placed in a way that uses sunlight as the main light and a reflector or supplimental light as fill, second, kicker, or hair lighting.

The fill light can also be used to separate the subject from the background by making the subject brighter than the background. One of the big advantages to using strobed light is that you can use the lens aperture to control the strobed light exposure of the subject, while using the shutter speed to control the ambient light exposure.

Here is an edit to kind of illustrate:

 

[DanFinePhotography]

I think on 2 and 3 your sensor was confused as far as it looks like the camera couldnt tell the difference between the cap and the sky. Solution? Get him a different hat, or meter from the sky