Hello Mallik,
Although I am not Rene, I hope I can help you out. From what I understand vector metrics are the metrics that in total make up the composite metric. For example Bandwidth, Delay, Load, Reliability, and MTU are the Vector Metrics. Together they are used in a formula to find the composite metric. This composite metric is used by EIGRP to decide the best paths to insert into the topology and routing table.
Below is a quote and link to a Cisco article that you might find helpful.
"EIGRP Composite Cost Metrics
The Enhanced Interior Gateway Routing Protocol (EIGRP) uses bandwidth, delay, reliability, load, and K values (various constants that can be configured by a user to produce varying routing behaviors) to calculate the composite cost metric for local Routing Information Base (RIB) installation and route selections. The EIGRP composite cost metric is calculated using the following formula:
EIGRP composite cost metric = 256*((K1Scaled Bw) + (K2Scaled Bw)/(256 – Load) + (K3Scaled Delay)(K5/(Reliability + K4)))
EIGRP uses one or more vector metrics to calculate the composite cost metric. The table below lists EIGRP vector metrics and their descriptions"
I hope this helps you understand EIGRP better!
Thanks,
Scott