1. A method for providing global load balancing by an appliance among heterogeneous load balancing devices, the method comprising the steps of: (a) obtaining, by an appliance, a first set of one or more metrics from a first load balancing device via a predetermined metric exchange protocol; (b) identifying, via the appliance, a second load balancing device, the second load balancing device comprising a different type of load balancer than the first load balancing device; (c) obtaining, by the appliance, a second set of one or more metrics from the second load balancing device via a network management protocol, the second set of one or more metrics different from the first set of one or more metrics; (d) determining, by the appliance, a load of the first load balancing device and the second load balancing device based on a first metric established by the appliance and a second metric selected by a user from one of the first set of one or more metrics obtained via the predetermined metric exchange protocol or the second set of one or more metrics obtained via the network management protocol; (e) receiving, by the appliance, a request to access a service on a network provided via one of the first load balancing device or the second load balancing device; and (f) transmitting, by the appliance, the request to access the service via one of the first load balancing device or the second load balancing device based on the determined load.