A new feature has been available in preview on Azure to help you analyze usage trend and diagnose issues with your storage account.

You can access Storage Metric from the portal or use REST API.

From the portal access the storage account you want to gather the metrics and access the Metrics blade; you will be able to export the results to an Excel file or/and configure alerts

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NOTE you also have a Metrics option available for classic storage account but this does not provide the same level of information/functionality

More details available at (especially for the Rest API use) https://docs.microsoft.com/en-us/azure/storage/common/storage-metrics-in-azure-monitor