You can sound the alarm
You can call out your guards
You can fence in your yard
You can hold all the cards
But I won't back down
Oh no I won't back down, oh no

from Eminem (Ft. Pink) – Won't Back Down Lyrics on Rap Genius

Meaning

You can do all these things to intimidate and/or upgrade your defense but Pink(or Eminem) will not back down.

Eminem (and/or Pink) can outmatch anyone, even when in the underdog position. No intimidation tactic or addition to your forces will work. Use of the modal auxiliary verb ‘can’ shows possibility but contrasts with the word ‘won’t’ which is definite. Either way Em and Pink are stronger than you.

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