There are 9 letters in "Metallica", so there would be 9! = 9*8*7*6*5*4*3*2*1 = 362880 different permutations; however, this is only the case if we could tell the letters L and A apart.
We have two copies of each of those repeated letters, so we have to divide by 2!*2! = (2*1)*(2*1) = 4 to account for these repeats.
Because we can't tell the repeated letters apart, we really have (9!)/(2!*2!) = (362880)/(4) = 90720 different permutations.
