So, Smaug was NOT the last dragon in Middle-earth. However, he was probably (in Tolkien's mind) the last GREAT dragon in Middle-earth.
Although Smaug was the greatest of the Dragons of his day, he seems not to have been the last of his kind as Gandalf told Frodo Baggins that "there is not now any dragon left on earth in which the old fire is hot enough [to melt the Rings of Power]", indicating the presence of other, lesser dragons.
He Was The Last Great Dragon
Tolkien confirmed in a letter that Smaug was the last of his kind; and the last of the Great Fire-drakes of Middle Earth. This implies that dragons of lesser stature, such as smaller Cold-drakes or Fire-drakes, may have lived on.
Was Smaug the last Dragon in Middle Earth to live or are there perhaps more dragons out there yet unseen? No, there were many. They lived in the Withered Heath to the far north. They drove the Dwarves out of the north.
Smaug- The last Fire Drake in all Middle-Earth. Killed by Bard the Bowman.
Smaug was perhaps one of the dragons that infested the Grey Mountains. Details of his origin are unknown, but he apparently was considered still "young" by himself and Gandalf when he first appeared in Middle-earth's history in T.A. 2770, and as having transitioned to become "old and strong" by T.A. 2941.
Smaug's dragon-fine would not have been hot enough to destroy the One Ring. The malevolence that Sauron put inside of the Ring could only be destroyed in the Cracks of Doom, so Frodo was compelled to make the journey to Mordor.
Smaug was the last of the great dragons, thus ridding Sauron of a possible powerful ally. Beyond this, all the rest of the dragons in middle earth supposedly only lived far to the north; being now a lesser race, the logistics of bringing them to bear, particularly in the southern campaigns, would be unlikely.
Although both the Balrog and Smaug are creatures of fire, and Gandalf is able to match them thanks to the power of his fire ring, defeating the Balrog takes far more spiritual prowess, which is why Gandalf is able to essentially 'level up' and comes back as Gandalf the White, whereas defeating such an immense physical ...
Basically, no. Drogon is a very young dragon and still barely large enough to get Dany into the sky… Smaug is gigantic, not to mention that Smaug talks and would probably have an intellectual advantage.
Smaug sensed Bilbo's presence immediately, even though Bilbo had rendered himself invisible with the One Ring, and accused the Hobbit (correctly) of trying to steal from him.
Drogon Daenerys Targaryen's mount from Game of Thrones, ended up being 50 meters long, plus or minus 10. Smaug from The Hobbit is a staggering 140 meters long, give or take 15.
The movies didn't show it, but the Balrog all but defeated Gandalf in a battle of spells. So, the bottom line is that some brutish beast like Smaug (regardless of his size) wouldn't have been a threat to a Balrog. The only thing that could save Smaug would be his wings -- if he flew away in full retreat.
Smaug was the first human to befall of Eve's powers and turned into a dragon. Smaug was Eve's strongest children and he and the other Alphas lead Eve's monster army.
The books already tell us what happens after Smaug is killed and the Dwarves reclaim Erebor. The Dwarves became prosperous again in the mountain but, as before, horded most of their riches, with some trickling out through trade with Men from nearby settlements.
If Smaug was born in the First Age, he should have been at least 6,212 years old at his death and he wouldn't have been "young and tender" at the falls of the two cities as he said he was.
God is the most powerful entity in Tolkien's Lord of the Rings universe. The Elvish name for him is actually Eru Ilúvatar, meaning “the one, father of all.” So the question becomes: Who is the second-most powerful being? Originally, it was Melkor, “he who arises in might,” the most powerful of the Ainur (or angels).
There is no direct link between Smaug and Sauron, but there is an indirect connection. Back in the First Age, Sauron was Morgoth's chief lieutenant. In this same period Morgoth bred the dragons, with the mighty Glaurung being the first.
Being as Gandalf could have thrown down Smaug, there are good reasons that Gandalf chose to take the roundabout way to the dragon's destruction. First off, it simply wasn't his job and doing so would have bordered on breaking the mandate of the Istari.
Smaug was considered to be the last "great" dragon of Middle-earth. Sauron allied with Smaug and intended to use the dragon's powers against the people of Middle-earth.
He wouldn't be attracted towards the ring because of it's power because Smaug believes he is the most powerful. He doesn't needs The Ring to be more powerful.
As a Valar, Morgoth led a whole slew of Balrogs in the First Age, but because Sauron was only a Maia, the Balrog would have had no loyalty to him. He was his own master in Moria, and no Dark Lord was going to ruin that. Thus, if he really wanted to recruit the Balrog, Sauron would have had to dominate it first.
Smaug is red and gold, with fiery breath, sharp claws, and a hide as strong as a diamond. Bilbo is horribly afraid, but he works up the nerve to take a single golden cup from one of the piles.
While there is no official answer for why Bilbo and Sam were able to be rid of the Ring without too much issue, there is a lot of supporting evidence that suggests it was partially due to their inner morality, as well as partially because of the Ring choosing its own path.
Thus, Smaug's embodiment of greed is based in history. From an in-universe perspective, dragons in Middle-earth regularly hoarded gold, and that trait is rooted in their very origin.