It is used by metal fans as general symbol of the affirmative, which could be anything from "hey man" to "fucking awesome" to "later"
it has recently begun to be used by people who are fans of other music genres and simply believe it is trendy to do. These people ar posers and are beneath notice.
annoying girl poser 2: OMG!! fully siiiiiiiick!!!!!!!!
annoying girl posers 1 & 2: WICKED!!! \m/ (both salute)! ROCK ON!!!!
shaka is a hand gesture with 3 fingers in the middle closed and having the pinky and the thumb stick out. This gesture has multiple meanings which originated with 'hang loose' or chill, relax, and is also used to give praise, approve, or to simply say thank you.
'ey, thanks braddah \m/'
thank you for your time,