Soundwave has served as a loyal Decepticon under Megatron and Megatron's command only. He also is the communication officer. His best fight is with his Minicon Army (Laserbeak, Ravage, Frenzy, Rumble, etc.).
When Megatron launched an assault on an orbital station commanded by the "Autobot" Starscream, Soundwave led a troop of Decepticons and gained control over a portion of the station, turning it into Megatron's command post. When Megatron arrived, Soundwave informed him, Brawl, and Barricade that Starscream locked down what was left of the station under his command from Decepticon reach. He also told Megatron he sent advance teams to clear the way for Megatron and his mini-squad. After Starscream and his fellow Seekers reactivated the Energon Bridge that fed the orbital station power to manufacture more Dark Energon, Soundwave informed Megatron that the Dark Energon was manufacturing at maximum efficiency. Megatron, pleased, then ordered a full-scale assault on the Autobot city of Iacon, where Zeta Prime and the Autobots guarded the Omega Key, which opened the way to the core of Cybertron, where Megatron would then plant Dark Energon to gain control of Cybertron itself.
After the demise of their glorious leader by the hands of the Autobot Titan, Soundwave, along with his Minicons, were able to successfully, fix Megatron.