they make a picture look good. Let us see how.
The above picture has a white thumbtack on a red background. The subject in the photograph is the thumbtack, but unfortunately it has a distracting red background. However, is there something that indicates that the thumbtack is the subject? A leading line pointing/leading towards the thumbtack could have helped.
I just had a red card paper and I used it in the above picture. I had a few more colored card papers, that were placed one above the other that created a line, just like the picture below
Although, the 2 pins are the main subject(s). A leading line was created (by overlapping the card paers at some point), but it is not really a leading line because it is kinda far from the subject(s).
Point: If you don't have a leading line you create one.
Let us see another example below, this one is closer to the subject(s).
This one was much better, and it won an award in a photography competition too. The choice of colors (red and green) could have helped too as they are complemetary in nature according to a color wheel.
So much for leading lines; generally lines add to the beauty of a picture and they are almost everywhere.
The below flower has lines on it's trumpet like body
Here is a denim button, that is the subject. It has leading lines going near it, but the macro beautifully captures the texture of the denim that has a lot of lines.
If you can show such things you should.
Camera: Canon 1200D
Lens: Tokina f2.8/100 mm macro lens
card papers of different colors
A pair of denims
Internet: search for color wheel