The Multiply Blend Mode can be used for a trick in blending. If you have a photo with a completely Black or dark background and the other with a light background color it is very easy to blend them in Photoshop.
Here is a free stock image of a candle. It has a black background.
Here is a free stock image of a candle. It has a black background.Here is another free stock image of a girl with a white background.
The girls photo has been blended with the candle in just a few, easy steps. You can do it too.
The tutorial is here.
Other tutorials are here.
