The motive of writing this post is to let all the movie goers to have a quick reference to the robots featured in the movie - either before or after watching it.
Believe me, as mentioned in my movie review - this movie can be confusing. I thought it would be beneficial for you to understand who's fighting with who in the movie.
In fact, I learned a lot about who's who in the movie, after I wrote this post.
If you disagree, please close this post immediately, else, don't wallop me. :P
Name: Optimus Prime
Alternate Mode: Peterbilt 379 semi-truck
Quick Info: Big boss of Autobots
Alternate Mode: Chevolet Camaro
Quick Info: Guardian of Sam Witwicky
Name: The Twins (SKIDS & MUDFLAP)
Alternate Mode: Ice Cream car (and later red Chevrolet Trax and green Chevrolet Beat)
Quick Info: Irritating twins that look like monkeys but did a good job to defeat one of a big bad guy(robot)
Alternate Mode: Yellow Hummer H2
Quick Info: The medic who helped to repair Optimus Prime
Alternate Mode: GMC Truck
Quick Info: The first Autobots to transform into robot to fight with Decepticons
Alternate Mode: metal silver Chevrolet Corvette Stingray
Quick Info: The one who slashed the Sideways (a silver Audi R8) in the early of the show
Alternate Mode: a pink Ducati superbike, a blue Suzuki B-King 2008, and a purple MV Agusta F4
Quick Info: Ridden by 'hot chicks'
Alternate Mode: Chevrolet Volt
Quick Info: He uses his "electro whips" to surge power from Jetfire to Prime so they can combine in the final battle.
Name: The Fallen
Alternate Mode: Cybertronian Jet
Quick Info: The big boss of Decepticons in this movie
Alternate Mode: Cybertronian Jet/Cybertronian Tank
Quick Info: He was revived by Constructicons & Scalpel under the deep sea.
Alternate Mode: F-22 Raptor
Quick Info: The coward who would always flee (and proved to be a good idea in the end)
Alternate Mode: Cybertronian jet/satellite
Quick Info: The robot which tapped into the human satellite. He also hacked the TV tower to broadcast the Fallen speech.
Alternate Mode: Mechanical scorpion
Quick Info: Killed by Jetfire
Alternate Mode: Missile
Quick Info: The machine which was destroyed by Bumblebee
Name: Scalpel (aka The Doctor)
Alternate Mode: Microscope
Quick Info: He was the one examined Sam in the movie.
Alternate Mode: Seven different pieces of robots (Scavenger, Hightower, Long Haul, Mixmaster, Overload, Rampage, and Scrapper.)
Quick Info: H-U-G-E
Alternate Mode: Helicopter
Quick Info: He was the one who captured Sam, Mikaela & Leo
Alternate Mode: Terex O&K RH400 Excavator
Quick Info: He's the one created big buzz in Shanghai!
Alternate Mode: Caterpillar D9 Bulldozer
Quick Info: The one who captured Sam's parents in Paris
Alternate Mode: Audi R8
Quick Info: He was killed in the car form by Sideswipe
Alternate Mode: ???
Quick Info: I'll leave it for you to discover. I must say, its tongue was quite disgusting.
There were some Decepticons-turned-Autobots characters as well:
Alternate Mode: SR-71 Blackbird
Quick Info: One of the cool member that helped a lot on Optimus Prime
Alternate Mode: Remote-controlled monster truck
Quick Info: One of the integral member who helped to locate the Matrix
After reading this post, if you still feel that it's confusing - good luck when you watch the movie.
ii) Rotten Tomatoes