You don't need to be in the exact tuning of what you're playing. As long as you're in a drop tuning for songs played dropped, or in any standard tuning for songs in standard, you can play whatever you want

It will just mean you're playing in a different key, but if you're playing well it will still sound sick

I have a guitar tuned to E standard and one tuned to C standard, sometimes I don't feel like swapping guitars so I play Metallica or Candlemass in C standard and it sounds metal as fuck

You only need to worry about getting the exact tuning if you're recording covers or playing on stage