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 meetings set by sales rep (for the month of June) which i being charted on the x-axis. In this scenario - we would like to have the reps names running across the x-axis (as opposed to June). 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. Note: you are only able to chart the metric name on the x-axis for Column and Bar charts.
After you click "Metric", click "Save" in the top right corner and your chart will be good to go.