Golem is a bipedal tortoise-like Pokémon with a spherical body covered by a shell of plated, green rocks. Its body is so hard that even dynamite cannot scratch it. Its head protrudes from the center of the shell. The head has a flat snout with two pointed teeth in the lower jaw and red eyes. It has short arms that have three claws and two legs with feet that have four claws in front and one in back. The head and limbs are light brown in color. Golem grows bigger by shedding its skin once a year. The discarded shell immediately hardens when exposed to air, crumbling away and returning to the soil. However, it stops shedding with age and moss grows over its shell. As shown in the Pocket Monsters Carddass Trading Cards, Golem's shell is hollow.

The anime has shown that Golem is able to withdraw its head and limbs into its shell and roll at high speeds. It is dangerous when doing this, as it is unable to see and may crash into or run over anything in its path. To prevent it from rolling into the homes of people downhill, grooves are dug into the sides of the mountains to divert the rolling Golem's course. It is seldom seen in the wild. However, it can be found living in mountainous regions.

In the Alola region, Golem has much shorter forearms with two claws. The feet have only two claws as well. Its face attracts iron sand, creating the appearance of a mustache, eyebrows, and a large black beard. Jutting out of the top of its body are two large, black rocks with a smaller rock in-between, forming a shape of a cannon. On the inner edge of the larger rocks are three golden dots. The cannon prevents them from easily rolling into a ball like its Kantonian variant. Alolan Golem is capable of firing the small rock by using magnetism. The rock will be electrically charged, creating shocks across the whole area of impact. Numbness and fainting can occur with even a glancing blow. If rocks are not available, it will fire nearby Geodude instead.