In this third installment of a four-part series on monitoring Docker, the focus is on the methods of collecting Docker metrics, highlighting three key mechanisms: pseudo-files in sysfs, the stats command, and the API. Each approach has its own strengths and limitations in terms of the types of metrics they can access, such as CPU, memory, I/O, and network metrics. Pseudo-files offer a fast and lightweight way to access metrics without needing root access, though they have limitations regarding I/O and network data. The stats command provides a continuous live stream of basic metrics, enhanced in version 1.9.0 to include disk I/O metrics, while the API offers a more detailed live stream of metrics, accessible through local connections with potential for increased flexibility via custom socket bindings. The article emphasizes that while these tools offer valuable insights, they may not suffice for production environments, where a dedicated monitoring service is recommended for comprehensive system health and performance tracking.