What is the best HEAVY METAL speaker?

Most any ohm Walsh suitably sized to room with appropriate amplification.

Having an amp more than up to the task helps with loud music. Avoiding any clipping at any time is always a good strategy.

In practice, if its truly good at classical its probably also good for heavy metal.

But the technical difference that classical music tends more towards dynamic peaks whereas heavy metal played as intended tends to be more consistently loud. Continuous delivery of power is not the same as delivery of peaks. If the amp can do both whenever called upon with the speakers used at the volume desired, then you are in good shape. Most good quality modern gear matched and set up optimally with those specific goals in mind can probably do the trick. If your amp is even slightly underpowered for the task at hand, and even subtle amounts of clipping occurs maybe not.

Clipping is always public enemy # 1 for good sound, its just that heavy metal, and large scale works of any kind, like big band jazz or classical/orchestral ups the ante.

The boundary between good sounding heavy metal and an ear bleed is a fine one. Keep clipping out of the picture and chances are best for good results.

"That's just the way it is, regardless (for the most part) of the music genre. If you want electronia to sound its best with all the bass impact, you need exactly the same thing."

That is true.

Of course its always hard to define what is good and what isn't. In this case its better to talk about performance in regards to ability to deliver the most challenging musical passages at high volume. You will probably almost pay more for better performance on a larger scale, but what sounds "good" or not is subjective and way more up in the air.

If you are reproducing music only on a small scale and with limited volume, then the world is your oyster. :-)

Atmasphere, you play a real Mellotron? Do they still make those? Do you maintain it as well?

Atmosphere, very cool!

I would think you and the mellotron to be a natural pairing.

ii have found assuring clean noise free power to be key for good sound with edgier music like heavy metal in particular. ⚡️⚡️🎸🎶🎶

I would take on most comers with my setup and OHM 5s, at least on my home court or in a similar fair home venue. Maybe not in a large auditorium or arena though. I would defer to the high efficiency horns for that.