There is something inherently cheesy about Hetfield's style of pronounciation both in "Kill 'Em All" (my absolute Metallica favorite) - kinda too "unintelligible" - and the Black Album - the continuous "hahas" and "yeas".
Although I can't really say that amounts to anything "embarassing" - as it's all done with a good portion of humor and irony, and is incredibly fun to listen to.
I guess I don't know any "embarassing" metal albums, lol. Shutting my hole right now.