The term, true metal, was invented by the popular heavy metal band Manowar in the nineteen eighties. Manowar invented this term because of the rising popularity of Glam metal. Also, during the eighties and the nineties, new metal genres came into existence. These new genres (such as: nu-metal, alternative metal, and metal core) were said, by Manowar, to corrupt the true spirit of heavy metal.

True metal is music that's true to the style of classic heavy metal. It's not diluted. It's not pussied out. It's not wimped out. It's played from the heart, 100 percentJoey DeMaio(manowar bass guitar player).

Manowar has shown respect for extreme metal bands, Venom, Celtic frost, and Mercyful Fate. They have also stated that the band, Immortal (which is a Norwegian black metal band), plays true metal. Although this is quite funny since Iron maiden member, Adrian Smith, was once asked if he liked Norwegian black metal. To which he replied, “No! Death to false metal.”
Death to false metal also happens to be a common saying by Manowar, because of its reference to true metal. So it is actually quite contradictory.

Note, for those of you that are not familiar with this sort of music: This genre of Metal is not about Satanism or gloomy things like that. True metal is just the opposite of that. It is a call for all of mankind to stick together to face oncoming difficulties.
“We shall live together as brothers, or perish together as fools.” As Martin Luther King once said and weird as it may sound to some of you. This is the true spirit of Heavy Metal. Do not judge others. Do not stick to the flows of fashion, but act by your own judgment. Form your own opinion, do not follow blindly the advise of others. Yet Mankind must stand together to face difficulties. It is this vision of absolute strength through friendship that this music represents.

“The brothers of metal will always be there. Standing together with hands in the air.” Quote by Manowar.

What also expresses this particular sentiment (part of Manowar’s song: heart of steel):

"Stand and fight
Live by your heart
Always one more try
I'm not afraid to die
Stand and fight
Say what you feel
Born with a heart of steel

in this case you can see quite clearly how serious they are about their music. For as they say, your opinion is worth fighting for. It is even worth death. As long as you live by your heart and steel yourself against those who don’t appreciate your opinion, you are born with a heart of steel.

Although I’ve made this largely about Manowar, the term true metal is however also used by Death metal fans, Black metal fans, etc… Of course in some (most) of these cases, the meaning of the term True metal changes and it means simply: “we are hardcore fans of these dudes on stage and we like their music.” You see? It’s not the same. It doesn’t carry a message saying anything of true metal value.
I’m sure that the lyrics have a message hidden in them. But since it doesn’t carry the same message as Manowar’s original theory of true metal, it cannot (in a way this is my personal opinion) be called thus.

I found an example of this on the internet where they assembled their top 10 bands that played true metal (according to them!):

  1. Iron maiden
  2. Metallica
  3. Children Of Bodem
  4. Slayer
  5. Blind Guardian
  6. Megadeth
  7. In Flames
  8. Amon Amarth
  9. Iced Earth
  10. Opeth

Now you see, Metallica (at the least) shouldn’t be in here for they are know to be a commercially corrupt band (this is not my personal opinion but a generally known truth). I don’t even mean this in a negative way. They can still make great music, but since it is commercial, it can certainly no longer (if it ever could be) be called true metal.