To pass dynamic values from a website into Google Analytics Custom Metrics using the data layer, which of these must be set up?

To pass dynamic values to Google Analytics Custom Metrics, you need three components. First, the data layer must be implemented on your website to store the dynamic values. Second, a Data Layer variable in GTM is required to read these values from the data layer. Finally, a Google Analytics tag must be configured with a Custom Metric to receive the value from the Data Layer variable and send it to Google Analytics. A Trigger is necessary to fire the Google Analytics tag but doesn't directly facilitate the passing of dynamic values into the Custom Metric itself.