If you don't like jazz, you won't get Jaco.
If you don't like Motown, you won't get Jamerson.
If you don't like metal, you won't like Harris.
One of the first metal bands I listened too was Iron Maiden, Piece of Mind to be specific, and the bass jumped out at me, even though I didn't know what a bass was. His tone and playing is really what drove their music for the first 6 albums. Then I saw a VHS of Live After Death and I wanted to play whatever that guy was doing. Done.
The man has incredible technique and presence in a genre not known for great bass players, unlike funk or jazz where every player is a monster. Plus he writes a large percentage of Iron Maiden's material. Coupled with commanding stage presence, it is hard for metalheads not to love him. Like Geezer Butler, it is very hard to explain the love for him, his playing either speaks to you or it doesn't; but when it does it is loud.