This is a pretty common question to a Scrum Master. Below are a few points based on current industry expectations.
#1 Now Scrum Master is no more a non-technical person who runs a few Sprint ceremonies, he is also responsible as Project Manager, QA & Technical Manager, who takes care of the Quality, technical & Product requirements. If possible he plays the role of BA also.
The more knowledge you have the better control you will have.
#2 Track & Resolve all impediments.
#3 Motivate & guide the team on better planning, and process following.
#4 Understand the team & have mental connection.
#5 Arrange all required training.
#6 Takes care of quality in each & every stage of the development cycle.
#7 Conduct all Sprint & other Ceremonies.
(1- Backlog Refinement 2-Sprint Planning 3- Daily Scrum 4-Sprint Review & Demo 5- Retrospective)
#8 Before Daily Scrum, make sure Jira’s status is updated with the latest update in the comment section.
#9 Sprint Capacity Planning & make sure 100% allocation.
#10 Make sure team members leave should not hamper the Sprint Commitment.
Motivate to convert unplanned leaves to planned leave.
#11 After meetings, review demo, note down MOM with action item & owner. Circulate the same with required Stakeholders.
#12 End-to-end (E2E) responsible for Software Development Life Cycle (SDLC)
Starting from Project Planning to Production Release.
#13 Find all possible solutions to smooth project execution, Quality control, Process & Performance Improvement etc which will give confidence to all stakeholders.
#14 Assist PO or BA on Product Backlog, User story writing.
#15 Create & maintain Jira Board & Reports.
#16 Before Daily Scrum go through all user stories & note down all points of action or discussion.
#17 Scrum Master helps in Hiring & Onboarding of team members.
#18 Scrum Master is SPOC (Single Point Of Contact) between the team & different Stakeholders.
#19 When the team raise any Clarification, Scrum Master makes sure the question is Technical to the point so, that others can understand without any further discussion.
#20 Scrum Master controls Scope change within the Sprint.
Still, if you are not convinced with the above activity then remember, in some teams & organisations, Scrum masters manage more than one team or project, two teams are pretty common to manage which is 50% allocation of the Scrum Master. All of the above activities will multiply two times.