Metrics in Scrum
What are the key metrics that a Scrum Master should consider
Why would a Scrum Master, on their own, consider any metrics?
What information are the stakeholders interested in? As a Scrum Master, I'd start there and then work with the stakeholders to make sure that they understand Scrum and empiricism, and then with the Scrum Team on ways to satisfy the information needs of the various stakeholders. Ideally, the team is able to find ways to radiate the information to the relevant parties on a frequent, perhaps even continuous, basis.
To what extent can those providing value use metrics which are important to them?
In my experience, stakeholders are primarily interested in:
"In the light of current / past velocity when can I expect a final product?"
They are only interested in burn down charts for the current sprint in the extent to which they shed light on this question.