The term "big 4" is being used to refer to a group of influential bands in the metal genre, with some outlets specifically focusing on 1980s metal. However, there is disagreement over which bands should be included in this group, with some arguing that certain bands, such as Testament, should be part of the "big 4" while others exclude them. The definition and composition of the "big 4" appears to be unclear and potentially subjective, with different outlets applying the term to different genres and time periods.