Optimus Prime is indeed the truck, and is the legendary leader of the Autobots (Good guys.)
The yellow car's named Bumblebee, and he's the 'cute' Autobot, the one that can easily mingle with humans.
The airplane's named Starscream, he's the Second-in-Command Decepticon (Bad Guy.), and my fave, cause he's always trying to overthrow Megatron, the Decepticon's leader.
And that black and grey monkey robot..... I think you're talking about Ironhide (The one doing the slow-motion spin while shooting from one of his mounted arm-guns in the trailer.) He's the Autobot's weapon specialist and war-veteran. He believes that 'High-tech circuitry is no replacement for guts.'
For further info, look on these sites:
The official siteA forum thread with leaked picturesBe aware in the forum thread, that during production, some designs have changed. I know for a fact that both Megatron and Jazz had some changes.
Update:
Okay, Transformers now is
definately in my fave movies ever list. It was soooo awesome. Go Blackout! People in the cinema were actually chanting his name,
and he deserved it! Man, this movie was such a rush..... I'm still shaking (No,really, I'm shaking while I write this.)
This post has been edited by P-girl: Jul 6 2007, 7:49 PM