A 4-2-4 formation in soccer is four backs, two halfbacks and four forwards. This is another common formation you would see in a soccer match. You'll find it has many similarities and strategies as other formations. It is also very similar to a football formation.
Many formations lean toward having only three forwards, with two wingers and a center. However, with an extra player in the center on the offensive line, this means there is another person to make passes to the wingers for a shooting opportunity.
A coach may use this formation when he has a very strong group of forwards and defenders. Since there are only two halfbacks in case the ball starts to move closer to the opponent's goal, the forwards are responsible for maintaining possession up the field, while the four defenders are working to keep the ball out of their side of the field.
The two halfbacks must also be quick-moving and light footed. Since there are two of them, each is responsible for guarding the middle and their respective sideline.