There's a linkin park song that uses this expression, what is the meaninig?
'Odds' mean probability. "What are the odds" means 'what is the probability' some outcome will happen. This expression on its own means, "Let me tell you what the chances of various outcomes will be", that is, the person saying this will compare your outcome vs another outcome.
Etymonline says that the 'stack up' part comes originally from poker (gambling), when you bet a stack of chips and this is compared against the stacks (bets) of the other gamblers. Hence it means how the odds (probability of a win) will stack up (be presented, more chips on your side or your opponent's side?). "Odds stacked against" means the same thing but that 'fate' or the probability of an event is not favourable to you, i.e., it is against you and it is not likely you will succeed.
This phrase, when said to a person, usually means the speaker is confident they will win against the opponent, and is said like a warning or a deterrent. It is saying, let me tell you what will happen, you will lose, and I will win. Taking into account the lyrics of the song (if I am allowed to do so briefly), this is reflected in the lyrics when the singer says "you play hard, I play smart".
It means "let me tell you what will probably happen".
"The odds" refers to probability / gambling, it means the likelihood of one thing or another happening. If you flip a coin, the odds of it landing heads are 50%. "Stacking the odds" means taking some action to make one situation more probable than another. So, "how the odds gonna stack up" means "what is most likely going to happen".
Note that the word "odds" here means something different than odd/even even though it looks like the same word.