What is the most important and most challenging role a teacher plays?

I think that all at the same time the most important and most challenging role a teacher plays is being a friend to their students.
I think it is important to be a friend to your students, and I saw the teacher I did field work with do this. The students are comfortable with the teacher and they can play and make jokes together. But at the same time that can be hard because there does have to be a line between the teacher being in charge of the students and how friendly they are. I think the most important thing a teacher can do is find that line as quickly as possible with each of their classes so they can have a successful and also a fun year together.