Story is inconsequential for
Hot Wheels Battle Force 5. All you really need to know is Earth is part of a multiverse inhabited by the Vandals (animals) and Sark (robots). Along with the humans who inhabit our Earth, the three races race around worlds searching for keys to unlock portals to new worlds. The premise is no goofier than
Yu-Gi-Oh placing the fate of the world on card games, but it at least gives you some context for racing through different worlds and ramming other cars.
Battle Force 5 doesn't waste any time dropping you behind the wheel as Vert, the leader of the group, as he races through worlds rescuing the other members of the team, usually by racing their personal vehicles through one of the game's repetitive courses. Along the way, you can ram other racers and collect items, but nothing about the game is particularly challenging, at least outside the driving mechanics, which do nothing to utilize the Wii's controls.
All of the game's courses are built around the race-and-smash dynamic, both in the single player and multiplayer modes. Multiplayer at least offers the option of playing with someone (or three if you want to take turns), but does a little more than repeat the single player experience. Two players race to see who can get the key to the portal the most in five minutes. Consequently, five minutes is all the time you're likely to spend in the mode. There's no way to customize matches and, by extension of the shallow game dynamic, there isn't much to hold interest.