“Hard Rock” is a huge category. I put most 1970s mainstream rock in the melodic category, as it often sounds mild compared to 1980s and later stuff. Beyond Iron Maiden this includes Led Zeppelin, Black Sabbath, Lynyrd Skynyrd, Nazareth, etc.
I also put Groove Metal such as Pantera into the melodic category, plus whatever amorphous genre Tool belongs to. Even alt rock such as Sonic Youth, or the early Pixies when Kim Deal was one of two singers, can be melodic and hard at the same time.
Yeah, @Nuance and @ProfFalkin, Nightwish is great symphonic and melodic metal. If you go down that direction Yngwie Malmsteen has metal, Classical, and orchestral connections.