Rumen converts lignocellulosic biomass to high-quality food by virtue of the diverse microbiota. The composition of rumen ecosystem is influenced by various factors including diet, individuality, age, geographical location, post-feeding time etc. Earlier culture-based techniques could study rumen microbes partially for the cultivable microbes. But now it is known that about 90% of rumen microbes are unculturable and the knowledge that we have till now seems to be limited. With the advent of new technologies such as next-generation sequencing which studied the whole ruminal ecosystem at one time contributed tremendously to our existing knowledge. Approaches like metagenomics, metabolomics etc. have made it possible to study the structure and function of rumen microbes in their natural environment. Understanding the composition and activity of the microbial community in the rumen is crucial for the improvement of productivity and lessening of environmental pollution in the ruminant livestock industry. Analysis of metabolome and microbiome revealed direct or indirect association for a better understanding of the biochemical and microbial functions of the rumen.