The song "2x4" was the first "Load" song ever which Metallica played live.

Album:
Load

The song live:
It has occasionally been played live before the release of the "Load" album. "Two by Four" was played for the first time live on August 23, 1995 in London, England. The song was also a fixed part of the "M2K" tour setlist.

"Two By Four":
It was the original name of "2x4" when they played that song before "Load" has been released. They played "Two By Four" on several festivals during the summer of '95.

Interpretation possibility:
It's about unnecessary resort to violence.