What is his alt mode

 

Well - if JoBlo is to be believed, which is let's face it, likely - Megs is a (Cybertronian?) jet fighter.

 

Out of all his alt modes being a jet got to be the coolest.

 

It's rumored he'll be a jet which is being more likely at this point seeing as how the other rumors are true.

That said who's to say he won't be a triple changer and also turn into the dragon we saw on the poster a while back? Wouldn't be the first time he's done that.

 

A jet/tank triple changer would be cool (Earth vehicles not Cybertronians), a bit like TW, though people would only complain he should've been Blitzwing  

 

My guess is that he will be a dragon and a jet, akin to G1 Snapdragon.

 

why a jet he was on in the first movie

 

Exactly. That was the original Megatron, why wouldn't he want to be like his old self again?  

 

I still don't understand how Megatron is in this when Galvatron is him reborn and I don't get why he has a different look than before.

 

We'll have to wait and see!  

 

His robot form does seem he'll transform to a Cybertronian craft of sorts, and also a dragon.

But the Joblo leak saying he's a military Jet has yet to be seen. His concept art so far doesn't seem to have any human milatary jet parts.

 

He's not going to be a dragon. Someone thought the spiky bits on his heels looked kind of claw shaped, even though movie-designs have almost never had kibble incorporated like that. He's going to be a jet, if he were to be a dragon it probably would have been included in the rumours.

 

They are the same guy anyway

In terms of looking different: to sell new toys of course

 

Do remember there were several Galvatron prototypes. Each embedded with a virus that contained Megatron's personality. Unless Megatron's head was destroyed it is still running on residual Allspark Energon.

Post TF1 Megatron has been an undead Transformer all along as he didn't have a Spark. Which is why he couldn't heal properly. In Galvatron he made a copy of himself that didn't have the limitation of needing Energon or a Spark.

 

Is this fact?

 

Yes Scalpel in ROTF used the shard on Megatron's head not his Spark chamber as he had no Spark to speak of.

In AoE Cade makes an observation that Prime's spark is his power source. As we've seen in ROTF a Spark is a ball of Energon. Basically Megatron was a Sparkless Allspark Mutation rather than a proper Cybertronian. An undead TF running on backup data on his head.

Optimus was severely damaged in AoE but managed to heal himself as his Spark was still functioning. With a little help from Cade.

 

Yeah, I think is there is literally zero evidence that he transforms into a dragon. If anything, I think the dragon is the Knightship transformed, and that Megatron likely commands it to do so.

 

Heh, how about a dragon\Cybertronian gunship?

 

I have wonder that myself.

 

Most likely the alt form from 2007. Plus there has been evidence of 2007 Megatron in Transformers Age of Extinction.