Capturing NGINX metrics varies depending on whether you're using the open-source or commercial NGINX Plus version, and the specific metrics you need. Both versions can report metrics through status modules and logs, with NGINX Plus offering more comprehensive metrics via the ngx_http_api_module, including data in JSON format for better integration with external systems. Open-source NGINX provides basic metrics through a status page when the HTTP stub status module is enabled, while NGINX Plus offers additional metrics on bytes streamed and upstream systems. The logging module of NGINX allows for customizable access logs, capturing detailed data points like HTTP requests and response codes, which can be processed using tools like logstash and Fluentd. Monitoring tools such as Nagios and Datadog can integrate with these systems to provide continuous monitoring. Ultimately, the choice of metrics to monitor will depend on the specific needs and resources of an organization, balanced against the cost of implementation, with Datadog offering a unified integration to facilitate easy collection and monitoring of NGINX metrics.