My father has the complete Zep collection; I listened to them as well a lot throughout the years. Definitely like them and they were certainly an influence on metal - especially the 80's "glam metal" scene with bands like Whitesnake, Def Leppard, WASP etc... was very much influenced by the "Whole Lotta Love"-side of Zep - but compared to what's regarded as "heavy" nowadays, a lot of people regard them as just classic rock and not in particular heavy hard rock or metal.

I like the early ZZ Top stuff the best tbh, when they were still a full on blues rock band.