Modern slot machines use a random number generator (RNG) to determine the outcome of each spin. When you press the spin button, the RNG generates a random combination of symbols, and the reels simply display the result of the RNG's calculation.
The outcome of a slot machine is determined by a random number generator, so stopping the reels at a certain point does not affect the outcome. The odds of winning on a slot machine are based on the game's design and cannot be influenced by the player's actions.