While I agree that the bass is in the forefront of quite a few metal bands, your idea that a band isn't a band with a bassist is off. I can think of fantastic bands/ensembles in every genre that do not use a bassist.
A bit off topic, but there is a great belgian rock band, the Black Box Revelation, that is only one guitar and drums. They sound so full, bluesy and rock hard.
Some great black metal bands don't have bass, and I like that subgenre. Nothing wrong with it.
Mostly I am into power metal. And I noticed that a lot of bands don't have a regular bassist. They use hired guns for studio and live work. The great thing about it is that they have sometimes great supporting bass lines (that don't want to sound metal among metal guitars and overshadow them). The trade off is that it diminishes the importance of the bassist as person. As if they are not part of the band but just a tool (not the derogatory sense of tool).
And how the hell can you say metalbands don't have a bass player
A band without a bass player isn't a band!
Anyway, I hope you're not mad or anything at me, just felt a bit misunderstood at first.