The idea for this rifle was born after the 1967 war, when the Israeli Army decided that it needed a lighter and handier rifle than the FN-FAL. The Arab armies had used the AK47 with great success, and IMI decided that the action of that rifle was worth copying. The operating system on the Galil, therefore, owes alot to its principle military rival, and the first production batch actually used bodies made in Helsinki for the Finnish M82 assault rifle. They may also have used other parts, but the choice of the 5.6mm cartridge meant that most of the internal components had to be redesigned to suit the smaller dimensions.

The basic rifle can be fitted with a wide variety of accessories; a bipod allows steady and accurate shooting and permits automatic fire with reasonable consistency, and it also doubles as a wire-cutter. The flash suppressor on the muzzle also acts as a grenade launcher, and every rifle is fitted with luminous night sights. The Israeli Army uses a version with a folding metal butt; for other purchasers there are options of fixed wood or plastic butts. A shortened version of the ARM (the standard rifle) is the SAR (Short Assault Rifle) which differs only in the length of the barrel. While the Israeli Galil is in 5.56mm caliber, a version in 7.62x51mm chambering is also made for export; this, too, comes in standard and carbine forms.