Dropships came into common use in the latter days of the Great War between the Autobots and the Decepticons. While they are generally armed with an array of weapons, their main purpose is to carry ground-based Transformers from place to place, usually between battlefield. To facilitate exiting the vehicle, the troop carrying area is open at the sides, allowing the troops to simply jump out.
Starscream, Skywarp, and Thundercracker encountered a large Autobot dropship armed with mortars while traveling through the lower levels of Cybertron. It sealed off their route with a force field, and they had to fight off the Aerialbots it disgorged and then destroy the ship with a Dark Energon detpak to continue. Later Megatron and his men traveled to Iacon by dropship. Starscream and his Seeker troops shot down at least one Autobot dropship while their leader was making his way through Iacon.
After inadvertently activating Omega Supreme, Megatron's warship was grabbed and tossed around by the titan until it crashed. He and his men attempted to get to a dropship, only for Omega to destroy that one too. As Megatron and his men headed for some anti-aircraft defenses, Omega himself acted as a dropship, depositing Autobot troops to fight the Decepticons.
Dropships were used during the Decepticon attack on Autobot City when the Autobots were trying to launch the Ark. Many of them were shot down or simply swatted out of the sky by Metroplex. At one point an Autobot dropship was shot down, and Optimus took a break from ordering Metroplex around to help the survivors. Meanwhile, Sideswipe flew a dropship into the Sea of Rust to drop Jazz and Cliffjumper off, so the pair could hunt for Grimlock.
A dropship was part of the Combaticon plan to intercept an Autobot energon transport—Brawl would fly the dropship to a bridge to take out the supports. After they brought the transport to a halt, the other Decepticons started trying to board it in dropships, with little success since the anti-aircraft defenses were still operational. While Swindle took out said defenses, he made use of the Combaticon dropship's roof-mounted cannon to finish the job.
Following Megatron's resurrection, the Decepticons used dropships to reach the crater where Trypticon crashed, only for them to all be shot down by the Autobot defense systems.