If you categorise Melodic Rock as Ten , Heartland , Frontline etc then there is little scope for variation in your preception.
Rubber does rock but it has a poppy element so what ?
Re Metallica I never said they were melodic hard rock in terms of your supposed
definition. I just mean they have melody whether you like them or not.
If you try to limit the bands mentioned on the board to a very small number who fit neatly into your pidgeon hole then that's up to you, but I think most people who post here are intelligent enough to realise variety is the spice of life.
I don't remember ever seeing a rules list that said you can only post messages about bands with a specific sound.