Middle Lane: Kings and Queens of Burst

The middle lane is usually where ability powered nukers (AP carries) reside. Champions like Brand, Veigar, and Lissandra are high damage champions that reach an extremely high burst potential by combing all of their skills together and executing them in rapid succession. This champions flourish in the middle lane because their high burst damage allows them to burn down a target quickly during a gank or 1v1. Often time middle laners will also have some kind of crowd control ability, whether this is a stun, slow, or suppression. This helps the jungler get into position to pull off a successful gank.

A middle laner needs to focus on staying in lane as much as possible, because the experience they gain is much more important than gold in the early game. This is primarily do to the large amount of damage AP carries get when leveling up skills. This is their primary source of damage until the mid game where they begin  buying better items. This is not to say that gold isn't an important resource, because that is far from the truth. Any champion in any lane should always maximize their gold input by farming minions, the jungle, etc (unless this means that you are a support taking minion kills from one of your team's carries.)

When an AP carry has sufficient control of its lane, they are often able to roam and gank the other lanes. AP Twisted Fates will often use their ultimate to teleport to another lane and try to get a kill or at least push back the opposing lane. However, mid players have to be careful as leaving their lane gives the opposing AP carry a chance to push the lane and get a tower down, or farm the minions and give the turret kills instead.

An AP carries main role in a team fight is to find high priority targets such as the enemies ADC or opposing AP carry and burst them down, killing them, or at least pushing them out of the fight. As an AP carry it's important to keep a safe distance and save any kind of crowd control you have for these high priority targets.