It sold 90,815 album units in October according to Oricon’s monthly chart. For comparison, the #1 ranked album this month was PARADE by Hey! Say! JUMP, released on October 30th, with 189,334 in sales.
METAL GALAXY did not chart monthly in any other country.
It sold quite a lot less (and ranked below) when comparing to their previous album, METAL RESISTANCE, that one had ranked #4 and had 132,881 in sales for March 2016. Note that it released officially on April 1st, but Tower Records sold it early, so it only had a couple of days to do so. The #1 ranked album released on March 30th and sold 476,120 units.
As for April 2016, it ranked #6 with 48,147 sales. The #1 ranked album had sold 203,806. We will have to see how METAL GALAXY does in it’s 2nd month.