One of the biggest attractions in DC Universe Online is the PvP system. Players will by default be able to choose a PvP server if they want to combat people in open world PvP. However, if you're not a fan of being ganked every time you try to complete a mission on your way to Level 30, the PvE servers may be best.
It may not be full blown PvP, but if you go the PvE server route, you'll be able to push yourself into other PvP opportunities including Legends and Arenas – which allow you to join up with fellow players in 2v2 and 4v4 matches.
Legends are the most interesting aspect of PvP. As most players already know, you don't get to play as your favourite superhero or villain. If you could, it would be a confusing game as 2 million Supermans flew around running into each other. But, with Legends, you can take on the role of your favourite iconics heroes and villains in scenario battles that take place over the course of a period of time.
Most of the Legends battles require 2v2 or 4v4 and can be played as PUGs or with a team you've compiled. Another plus here is that the combat is available for players at level 8 and on, not just for Level 30 players.
The other form of PvP play is done by your main character – the hero or villain you created when you started playing the game. Arena play is done in the same bracket style of gameplay that you'll find in Legends though with a little less variety in the landscape when you play. So, if you're interested in playing the game in a more engaging manner, you'll need to find players who can join with you and create a long term team.
The best route here is to not just create an arena team, but to forge a League through which you can build experience with your fellow players. This will let you combat players in Legends and Arenas and make sure you always have a good group to call on when you need to go into a new Alert or Raid.
The PvP content in DCU Online goes above and beyond what most other established MMOs have done in the genre and it's a heck of a lot of fun to boot. So, make sure you approach it with the care and time needed to get as much out of it as possible.