To chart a metric name on the x-axis you will need to start in the chart editor as shown below:
In this example - we have quarterly data going back a year but we'd only like the show the most recent quarter with the metric name on the x-axis (as opposed to date). Once you have your metrics in place for the chart you will want to navigate to the "Options" tab:
From the "Options"tab - you will want to select the "Metric" button for the X-axis as shown above. We will automatically chart the most recent period of data you have tied to the metric name.
After you click "Metric", click "Save" in the top right corner and your chart will be good to go.