From Halopedia, the Halo wiki
The machete is a standard UNSC field issue tool for use in jungle environments. The machete's grip has a thin gel layer similar to that found on MJOLNIR Powered Assault Armor, a quad tier design to absorb shock from impacts and a unique layer design that enables the machete to self-sharpen with use.
The machete is featured as the sword found on the difficulty emblems for Normal, Heroic and Legendary difficulty in all currently-released Halo games aside from Halo 3: ODST and Halo: The Master Chief Collection, which replaces the machete with M7S SMGs and energy swords. It is given some in-universe flavour text in the menus for Halo 2's PC port alongside the UNSC shield.
During the development of Halo: Combat Evolved, a weapon bearing visual resemblance to the machete was intended for inclusion in the game. Known as the Pattern-2 Composite Sword, it is likely that the difficulty shield machetes are based upon this cut design.
List of appearances