When you begin learning photography, you are often told to keep the sun, or the light source behind you. Obviously the light should fall on the subject from somewhere near the camera’s point of view so as to illuminate it, right? While this is a good rule of thumb to apply when you are taking your first few portraits, once you have reached some level of control over your exposures and metering, it is time to experiment by breaking the rules.
Having your light source behind the model can give you some interesting results. Depending on how you position the light and meter off it, you could create an early morning feel as you see in this image of a couple by Karthik Srinivasan (photographed on SONY Alpha 7 Mark II, 70-200 lens). The mood and styling of the image coupled with the behind the light scenario depicts an early morning feel.
To create a high fashion glamour feel, you could tone the light down a bit, increase contrast and have the light source partially within the frame. While shooting outdoors, position the model so as to silhouette them against the sun, then meter off the face. You could even use a window light indoors for the same effect. However, do note that in most scenarios you will need an additional light source or reflector so as to illuminate the model. The intensity of this second light source gives you control over the final result and feel that you desire.