the answers
Jocie, I’ve left out the different drive effects you use and the details of what power supply, patch cables and guitar cables you use as I don’t want to point fingers at any one brand. This is logical as well as diplomatic, because a pedalboard actually needs to be considered as a system – any part of which will interact with and affect the others. This means that, although some pedals can be made culpable in one scenario for noise, in others they would be the benign partner.
So, the easy question first: do you need a noise gate? No, I don’t think so, not for what you’re trying to achieve with regards to reducing noise. Do you need one for some genres of metal? There is an argument that yes, you need one if your palm muting isn’t as clinical as you need for fast gated staccato chugging. Only you can decide this.
Now to reduce your noise issues. Start with the best isolated output power supply you can afford. This is a must as it will reduce signal/noise bleed from pedal to pedal. Remember, gain pedals increase the gain, so if noise is there at the power input, it’ll be much worse several stacked pedals later. Patch cables are seemingly benign items, but some can be noisy, microphonic and badly made. Buy decent patch cables and the link between pedals just won’t be an issue. The same can be said for guitar cables. You don’t need to go superexotic, but a low-noise, well-made guitar cable is a must.
As for pedal choices, I’d suggest that stacking four drive pedals is probably too much. You’d be better placed to stack two pedals and run the gains slightly lower. I know this sounds boring, but less is definitely more. After a certain point your sound doesn’t improve, it just becomes more compressed and heavily clipped in a square wave fashion (fuzz). Anything after this point just reduces the signal to noise ratio: namely, it is detrimental without adding anything beneficial. Something to consider is that often what metal players want is a tight or loose sound in certain frequency ranges. This can be achieved with a quality EQ pedal stacked after your drive choices. If you take these steps, you can craft the sound you want and remain in the realms of sanity with regards to ’board noise, hum and feedback. Good luck! Let me know how you get on.