Custom Metrics can have which scopes?

Custom Metrics in Google Analytics can be defined with either a Hit or Product scope. Hit-scoped custom metrics are associated with individual interactions on your website, like a pageview or an event. This allows you to track numerical data related to specific actions. Product-scoped custom metrics are used specifically for Enhanced Ecommerce tracking, allowing you to associate numerical data directly with individual products, such as a product's discount amount or a specific product rating. Session and User are not valid scopes for custom metrics; they are scopes for custom dimensions. Custom dimensions track qualitative data, while custom metrics track quantitative data.