What is the evolutionary role of viruses in nature?

Viruses adjust the course of evolution. Viruses, through pandemics, destroy and weaken certain phenotypes that are no longer involved in the process of evolution.
About 20% of human genetic material is introduced by viruses.
Sometimes viral genes become cellular genes.
Viruses can not only change the genetic apparatus of a cell, but also exchange genetic information within a species and between different groups of organisms. In a changing environment, this is a powerful evolutionary mechanism. That is, viruses stimulate evolutionary processes in the biosphere.