The purpose of this paper is to study the feasibility to utilize methane, which is the main component of natural gas and biogas, as a fuel for lean-burn engines. To realize this, however, there are mainly two problems to solve; the substantial decrease in the burning velocity and the large increase in the misfire probability in the lean mixture region. It has been shown that such problems can be solved by adding hydrogen to the lean methane mixture. By adding only a small amount of hydrogen to the lean methane mixture, the turbulent burning velocity is substantially increased and the lean limit is greatly extended, at the same time. Furthermore the condition at which hydrogen addition most effectively improve the turbulent combustion performance is identified. Finally these improving mechanisms are discussed.