| Mise en Abyme | Prog Metal | Gipuzkoa | |
| Mitosia | Rock/Metal | Bizkaia | |
| Mørgue | Thrashcore | Gipuzkoa | |
| Ms. Missery | Alt rock/metal | Bizkaia | |
| Mundo Rata | Thrash/Death Metal | Araba | |
| Mutilated Judge | Grindcore | Bizkaia | |
| My Sweet Torment | Black/Death Metal | Bizkaia | |
| NaizPresidente | Metal/hardcore/rock | Gipuzkoa | |
| Nakkiga | Pagan Black Metal | Araba | |
| NameOff | Rock/Metal/Hardcore | Araba | |
| Neila | Post Metal | Bizkaia | |
| Nekrocake | Death Metal | Bizkaia | |
| Neriva | Metal | Bizkaia | |
| Nessun Dorma | Metal | Bizkaia | |
| Ni Hil | Post Metal | Araba | |
| Nihilrage | Death Metal | Nafarroa | |
| NoisAlive | Heavy metal | Nafarroa | |
| Nox Larvae | Death/thrash metal | Bizkaia | |
| NTN | Metal | Nafarroa | |
| Nuclear Revenge | Black/Thrash Metal | Araba | |
| Nukore | Nu Metal | Araba | |
| Nulled | Metalcore | Araba | |
| Numen | Black Metal | Gipuzkoa | |
| Nunk | Metalcore | Gipuzkoa | |
| Nx | Rock/Metal | Nafarroa | |
| Obliterated Swarm | Death/Grindcore | Araba | |
| Obstetra | Death/Grindcore | Bizkaia | |
| Odolean | Black Metal | Nafarroa Beherea | |
| Oh, Leader! | Math/Prog Metal | Gipuzkoa | |
| Oneiric Delusion | Heavy/Prog Metal | Bizkaia |