The phrase "main man" is an idiom that is commonly used to refer to someone who is very close and important to you. However, there are several synonyms that can be used in place of "main man." Some of these synonyms include "best friend," "companion," "confidant," "partner," "buddy," "brother," "pal," "mate," and "sidekick." Each of these synonyms capture the essence of a person who is there for you during good times and bad; someone you can rely on without hesitation. Whether you use "main man" or any of these other synonyms, what matters most is the close bond and trust shared between two people.