Microsoft's Internet Information Services (IIS) is a web server that comes bundled with Windows and has numerous extensibility features. It allows for the use of various backend technologies like Flask, Node.js, and ASP.NET. IIS also supports modules to perform tasks such as URL rewriting and programmatic load balancing. Monitoring key metrics in IIS can help ensure its availability and performance. These include HTTP request metrics, HTTP response metrics, availability metrics, and resource metrics. By tracking these metrics, administrators can identify potential issues and optimize the server's configuration for better performance.