The music of Children Of Bodom is really melodic and fast paced with Death vocals, along with the rather technical guitar solos, catchy riffs and choruses, they are very easy to get into, thus their success.
Follow The Reaper is definitely my favoutite COB album. Alexi "Wildchild" Lahio is amazing on the guitars as usual, but what stands out to me in this album in particular are the keyboard melodies and its presence throughout in general.
Children Of Bodom doesn't really need much introduction as they are one of the most successful bands from Finland. Hatebreeder is their second studio album and is considered by many fans their best.