The "M" in the BEAM framework asks you to think about the lens (or lenses) through which you want to explore your research topic. Here are some questions to think about:
Are you investigating a question via the methodologies of a particular discipline or academic subject, like history, sociology, or religious studies? If so, is there a specific sub-discipline you'll be using? For example, in the broad discipline of history, some sub-disciplines are political history, cultural history, intellectual history, gender history, etc.
Is there a particular theory which you'd like to use as the frame for investigating your topic? This is often referred to as a frame and case approach, or case study.
Do you want to approach your topic through an interdisciplinary framework (integrating knowledge and methods from different disciplines)?
BEAM is an acronym intended to help you think about the various ways you might use sources when writing a researched argument. Joseph Bizup, an English professor at Boston University, outlined the framework in a 2008 article. The idea has since been refined and adapted by many others.