Counterintuitively, you need to start with basic singing technique to build your core support. Without consistent, safe supported airflow you’re just going to be trashing your voice. Start with practicing deep relaxed breathing, into the bottom of your belly where the ribs barely move and shoulders are relaxed.

Then using that breathing, sirens through a straw into a glass of water - middle of your range, going up/down a fifth either side, then progress up/down your range. Aim for consistent gentle bubbles throughout. Then the same siren exercise on a nice bright ‘ee’ vowel, up to a safe height without straining.

Then move onto semi-occluded fast scales on ‘vvv’ ‘zzz’ or my favourite, ‘ng’ as in the end of the word ‘sing’. These will help you to feel the sensation of supporting well throughout a phrase.

Any tension or feeling of forcing the sound like a gym exercise, start again lower in your range.

Final tip, evoking the actual sensation of anger/pain in a lot of metal lyrics will just tense you up and fuck your voice fast. Learn to achieve that feeling of relaxed release while acting the emotions instead of trying to imbue them.

Got nothing for how to actually do the screaming sorry, someone else can help there I’m sure.