Outside of the comics, Ares has appeared in Justice League Unlimited, the 2009 animated Wonder Woman movie and Injustice: Gods Among Us (to name a few), but the DCEU Wonder Woman movie has unquestionably been his most significant, public appearance.
Obviously the original deity Ares is part of ancient Greek mythology, but as far as the DC Comics mythos goes, the character was first introduced in 1942’s Wonder Woman #1, though it would be another four decades before he would regularly be called Ares rather than Mars.