Megatron has his arm cannon which can deal some intense damage in one shot. Teridax has many abilities of his own including teleportation, lasers, size manipulation, slow down, and many others. It would definitely be a good fight, but I think that Megatron may have this with his immensely powerful energon sword. Megatron wins.
DReager1.com 
His energon sword is strong, but I don’t know. Given the size of Mata Nui’s body, I don’t think Megatron will be able to injure him that badly. Plus
Teridax can grow to immensely large forms, but Megatron once took out an avatar of Unicron in one hit and those guys were also giant. Plus in G1, his Fusion Cannon’s strength is pretty immense and there was really no foe who could endure a shot from it once in Galvatron form. It would be a cool fight
With his energon sword you are right, Teridax would have little chance against Megatron. Even if he could still defeat him by the trick and strategy… But without his energon sword or another power up I think Teridax wins this fight easily.
Without the sword it could definitely get dicey, but Megatron’s cannon would also pack a serious punch in this round if he got the chance to fire it. Teridax is no pushover though so he won’t go down easy!
Yeah, the canon of Megatron could do considerable damage to Teridax. But teridax has some powers that could protect him from his attack like dodge, density control and he could also send back Megatron’s attack against him with his teleportation power. Teridax also control magnetism that could be a major impasse for him.
Magnetism could be tricky. I think Megatron’s Cybertronian elements should be able to protect him to an extent, but it would get dicey. Megatron would need to get up close to minimize Teridax’s dodging potential.
I just realized everything that Teridax could do to defeat Megatron is trapping him in an illusion at the beginning after, he teleports back to him and uses his molecular destruction power by touching him. After all, Megatron is inorganic to my knowledge (correct me if I’m wrong) and as this power work with inorganic beings, Teridax will have a big advantage against him.
I think Megatron may be organic or at the very least, he’s not purely inorganic. Cybertronian tech seems to virtually be alive, but it’s definitely a very gray line. I’m not sure about the illusion working on him though since Megatron’s will power is so strong.
I guess Megatron. This Teridax is a mere flesh and blood creature. Just like the average Cybertronian. For Megatron it’s Tuesday.
Yes, Megatron has taken on stronger opponents in his day and always comes out on top.
flesh and blood any more, the makuta all evolved into dark energy beings in armour
SAVE OUR SALAMI!!!