Metric tags are crucial for effective monitoring of large-scale and dynamic infrastructure, as they allow for flexible aggregation and observation of metrics across various levels, such as hardware profiles, software versions, and availability zones. In systems like Datadog, tags can be added to metrics on the fly, allowing for real-time updates and automatic metadata detection, which simplifies the process of identifying and responding to changes in infrastructure without needing to modify the data collection process. By using key:value tags, users can create new dimensions and attributes, which enables more detailed and customizable monitoring, making it easier to track performance issues at different abstraction levels. This tagging system eliminates the need for manual aggregation and complex naming conventions, providing a scalable solution suitable for the dynamic nature of modern cloud environments. Datadog also offers the ability to add custom tags programmatically, enhancing the flexibility and adaptability of its monitoring capabilities.