See the website: https://scalameta.org/metals/
See the contributing guide: https://scalameta.org/metals/docs/contributors/getting-started.html
To learn more about how Metals works, see ./architecture.md. It explains the high-level layout of the source code. Do skim through that document.
For more information on the current maintainers, companies that have/are sponsoring the development of Metals, and acknowledgements of previous work, please see https://scalameta.org/metals/docs/acknowledgements/development.html.
Metals = Meta (from Scalameta) + LS (from Language Server)