The metric value to compare to BreachThreshold. This enables you to execute a policy of type StepScaling and determine which step adjustment to use. For example, if the breach threshold is 50 and you want to use a step adjustment with a lower bound of 0 and an upper bound of 10, you can set the metric value to 59.
If you specify a metric value that doesn't correspond to a step adjustment for the policy, the call returns an error.
This parameter is required if the policy type is StepScaling and not supported otherwise.