Football cleats are essential for all players. In order to have traction on a grass or artificial turf field, players must wear cleats if they want to play their best football. Cleats allow a player to gain a toehold on the field and have leverage when they play the game. A player who takes the field without the ability to dig in will not be able to command his strength, speed and quickness in the middle of a play.
Your weight is leaning forward before the start of every play. Wearing shoes with cleats helps a football player maintain his balance and strength when he hits a player on the opposite team. When this player is an offensive lineman blocking for a running back, his block occurs at the point of attack. A player who does not have leverage at this spot has no balance and cannot help his team.
Football shoes generally have cleats that are about 3/4 of an inch long and about 1/4 inch in diameter. Plastic cleats are used on a grass field on a dry day. However, if the field is very wet and it is raining, players use even longer cleats to maintain their balance. When it is very cold and the field is starting to freeze, the players use shorter cleats, perhaps 1/4 to 1/2 inch long. If the game is on a frozen field or artificial turf, the player will trade his cleated shoes for ones with ripple soles that promote traction.
Spikes give football players a physical advantage and confidence. A player feels good knowing that it is very unlikely he will slip for no reason. That's what would happen if he played without cleats when performing on a grass field.
Sometimes conditions change within the game itself. It may start off sunny and the skies could open up and turn the field into a quagmire. In that case, players have a tool called a spike wrench that will take out the old cleat and allow them to screw in a new one in less than a minute. Players don't have to change their shoes; they just have to take out the old cleats and screw in the new ones.
Football cleats that are used on a grass field in good weather are spaced every 2 to 3 inches on the sole of the shoe. They are spaced that way to allow the player to move with excellent balance and confidence. Players without the proper spacing of the spikes on the bottom of their shoes will tend to slip.
There is a school of thought that says players may use their cleats as weapons if they get frustrated within the course of a game. This is very unlikely because teams are warned before the game about engaging in unsportsmanlike behavior. The stomping action would be very noticeable and players would be kicked out of the game and suspended from future action for such poor behavior.
The cleats used on football shoes used to be made of metal and players wore them on grass fields through the mid-1980s. The advent of plastic spikes allowed players to get better toeholds because they were round and symmetrical. Metal spikes turned out to be a liability in adverse weather conditions. Players could not dig in well on frozen fields and they offered little support in rainy conditions. The metal spikes were about 1/2 inch tall and were about 1/4 of an inch wide.