The Azure portal provides multiple monitoring options, which are available under the Overview | Monitoring | Support + Troubleshooting sections for an Azure SQL Database:
Let's talk about each of these options in detail.
Database metrics such as CPU percentage, DTU percentage, data I/O, and other metrics can be monitored through the overview section.
The overview section displays the DTU percentage from the past hour of an Azure SQL Database in the form of a line chart:
You can even pin the chart on your Azure portal dashboard by clicking on the pin icon in the upper-right corner of the chart.
This way, you can monitor the DTU percentage as and when required.