1. A computer-implemented method, comprising: determining, by a host controller machine, that one or more collected metrics have triggered a load balancing operation of the host controller machine; identifying, by the host controller machine, a plurality of source host machines and a plurality of virtual machines (VMs) hosted by the plurality of source host machines as candidates for selection by the load balancing operation for migration; and adjusting, by the host controller machine, a selection score for at least one of a candidate source host machine and a candidate VM based on one or more metrics of the candidate source host and of the candidate VM, wherein the one or more metrics are associated with one or more candidate target host machines to which a candidate VM could be migrated.