Is velocity a good metrics for measuring team performance or productivity

If you could provide more information, we might be able to give you better advice.  For example, how do you plan to measure velocity?  

Also, I suggest you search this forum because there are a lot of discussions on velocity that you may find helpful.

As defined in the Scrum glossary:

Velocity: an optional, but often used, indication of the amount of Product Backlog turned into an Increment of product during a Sprint by a Scrum Team, tracked by the Developers for use within the Scrum Team.

It really has two uses. t may be used by Developers in Sprint Planning to determine how many Product Backlog items (PBI) they should bring into their Sprint Backlog. It can also be used by the Product Owner to forecast when a PBI may complete or how many PBIs may get completed by a certain date.

It is not a measure of productivity or value delivered by a team.

For a good take on metrics check out Evidence-Based Management: https://www.scrum.org/resources/evidence-based-management

Is velocity a good metrics for measuring team performance or productivity

Can stakeholders put it to productive use?

Who is trying to use velocity as a measurement? What is the unit of measure of velocity that you are attempting to use?

If it's internal to the team, then it could be a good measure. However, I would avoid using it outside of the team. Velocity is highly sensitive to changes. Depending on your unit of measurement, it probably won't be standardized or normalized across teams.

Some more context about what problem you're trying to solve is necessary to know if velocity is a reasonable measure to give useful information.