If you have a report with more than one metric, you can change the arrangement of the Y-axis.
The default is separate scales for each metric, as below:
Merge or Move Scales
Click on the cogwheel, and you'l see Y-Axis management at the bottom of the current visualisation.
Click and drag metrics to rearrange the axis. You can either:
Merge - Drag one metric on top of another to merge the scale.
Move - Drag the Axis onto the header 'New Y-Axis on the Right'
It is worth considering whether the scales are of a similar range. Here it makes sense to combine Revenue and cost, and the move orders to the right axis to display the report more clearly.
Here, we have done both: