The term "Heavy" usually corresponds to the 800 or 900 weight range—thick, imposing, and impossible to ignore. However, the search term presents a bit of an oxymoron. A "500" weight is typically a Medium weight, which is slightly thicker than a standard Regular font but nowhere near as thick as a "Heavy" font.
The Digital Architecture of ZAP Heavy 500 In the landscape of modern typography, the ZAP Heavy 500 zap heavy 500 font free download