Firstly, you're confusing metal with hair metal. Secondly, yes, some metal bands have cheesy lyrics that are just for fun, but that's all they are! Fun! Thirdly, before you attack my preferred genre of music, consider the following:
-Iron Maiden
Lots of their lyrics deal with literature, war, and history. Well-read and even turned a poem into a 13-minute epic.
-Death
Brought philosophy to the forefront and pondered upon life's mysteries, alongside calling out the spirit crushers amongst us.
-Sabaton
90% of their music is historical.
-Carcass
Features songs with words like "Necroticism: Descanting the Insalubrious", stuff you and most of the population have never heard of.
And these are only some of them. Also consider the technicality that's involved in playing this stuff.
What kind of music do you listen to? Can't be as good, well-researched, or FUN as metal.