Contrast is a metaphor, which compares two different things or two aspects of the same thing together.

For example, some people are alive but dead; Some people died, but he is still alive. (Cang Kejia, "Some People")

Using contrast, we must have a deep understanding of the contradiction of what we want to express. Two things to be compared or two aspects of the same thing should be opposite, otherwise they cannot be compared.

Contrast two corresponding things to make the image more vivid and feel stronger.