AWS Elastic Load Balancers (ELB) have been lacking in monitoring metrics since their introduction in 2009. However, with the recent addition of three new metrics - BackendConnectionErrors, SurgeQueueLength, and SpilloverCount - ELB monitoring has become more comprehensive. Essential ELB monitoring metrics include HealthyHostCount, Latency, HTTPCode_ELB_5XX, SurgeQueueLength, and SpillOverCount. Other secondary metrics are RequestCount, HTTPCode_ELB_4XX, and HTTPCode_backend_yXX. Composite ELB metrics can be computed by combining multiple metrics to better understand load balancer behavior. AWS CloudWatch metrics have a timeframe of 60 seconds, which is important to consider when monitoring counts per minute.