Yes, methane, especially from cows and livestock, is a contributor to global warming. Other sources of methane worthy of concern include oil and gas wells (apparently they leak a lot) and other quasi-natural sources like the breakdown of plant matter in forests (often because the forest is cleared).

Methane is far more potent than CO2 but also far shorter-lived. I would argue in many ways it's far less of a concern because it doesn't interact with plant and animal life to anywhere near the extent elevated CO2 levels do.

http://www.chicagonow.com/dennis-byrnes-barbershop/2016/12/r...