Generally speaking, wild symbols are mainly included to complete your winning combinations by substituting for other symbols except scatters and special bonus symbols that activate free spins, bonus on the reels and second screen games. They are created to significantly increase your chances to win, as compared to playing the old-style classic game that does not have such symbols.
It should be mentioned that standard Wild symbols have acquired more functions over time, becoming Expanding Wilds, Stacked Wilds, Random (or Wandering) Wilds and Multiplying Wilds. That is why once you meet any of the mentioned above wild symbols online, you will be absolutely delighted.
By the way, you can find an extensive list of slot machine games that include Wild symbols on this page. Play any of them to discover how the Wilds can improve your chances of winning. Once you give a try any of the slots, boasting a wild symbol, it is for certain that you will simply adore it. So, head for breathtaking emotions and good luck!