The euca2ools euscale-* commands are for use with the Auto Scaling service, the euscale-describe-metric-collection-types command is the DescribeMetricCollectionTypes action, and only returns metrics for Auto Scaling.
To enable EC2 metrics in Eucalyptus you have to enable metrics collection for the instance (euca-monitor-instances) and you should also ensure that when working with the CPUUtilization CloudWatch metric you specify the unit type of Percent.