Son'a were considered a narcissistic and materialistic people. They put great value in precious metals, rare jewels, and other materials the desire for which was thought antiquated by Federation standards. They raided inhabited worlds in search for these resources, and also for slave labor, especially females. However, by 2375 it was believed that this practice had ended.
Without the regenerative effects of the Ba'ku homeworld's metaphasic radiation, the Son'a became desperate in their efforts to prolong their lives by any possible means, including genetic manipulation and surgical techniques. The Son'a would make regular visits to facilities where their skin was stretched tight, and accumulated toxins were purged from their bodies. Nevertheless, due to the amount of bacteria entering their system, in the 2370s many Son'a (including Ru'afo himself) were suffering from fatal diseases and nearing death. It was also revealed that it would take at least ten years of normal exposure to the metaphasic radiation to begin to reverse their condition.
Some sociologists attributed their aggressive behavior to desperation, brought on by their infertility. On a more positive note, the Son'a were highly praised for their accomplishments in the arts, the high quality of their vinting and their "hospitable" attitude towards personal relationships.
The Son'a were originally Ba'ku, living on the idyllic Ba'ku home planet in the Briar Patch. In the late 23rd century a group of young Ba'ku desired to follow the way of the offlanders. They attempted to take over the Ba'ku planet, but failed and were exiled.
After a brief flirtation with space colonization, this group settled into a pattern of Nomadic acquisition. They would raid planets for resources and slave labor, and about half a century before 2375 subjugated the Tarlac and Ellora species to serve as indentured servants and soldiers. The Federation sanctioned them multiple times, and by the 2370s the slave raiding was thought to have stopped as a result.
By the 2370s, Son'a maintained colonies in the outlying areas near Cardassia and the Bajoran wormhole. By this time the Son'a had become infertile as well. The Federation speculated that this might have been the result of biological or genetic engineering. (Star Trek: Insurrection)
In 2375, a group of Son'a led by Ahdar Ru'afo attempted to access the metaphasic particles within the rings of the Ba'ku planet, now located within Federation space. To do so, they entered an alliance with Starfleet Admiral Matthew Dougherty, who convinced the Federation Council to approve the scheme. The Son'a had developed a metaphasic collector to harvest the particles, but it came with the secondary effect of rendering the planet uninhabitable. They agreed to follow Starfleet procedure and relocate the existing Ba'ku population beforehand, using a hidden Federation holoship.
The plan began to unravel when Lieutenant Commander Data from the USS Enterprise-E uncovered the holo-ship and was shot by a Son'a soldier. This caused him to malfunction and the Enterprise was sent to retrieve him. When the Enterprise arrived, they discovered the true nature of the Son'a's operations, the crew rejecting Dougherty's claims that the relocation of the small number of Ba'ku on the planet was worth it compared to the billions who would be helped by the subsequent advances in medical technology as they felt that the moral cost that would be paid in the destruction of the Ba'ku culture was too great. Captain Jean-Luc Picard threatened to expose this to the Federation, by sending Commander William T. Riker and the Enterprise to the edge of the Briar Patch to contact the Federation Council, while he and a number of his officers took the captain's yacht to the surface to help the Ba'ku. In response, Ru'afo sent Son'a warships to intercept the Enterprise and ordered the Ba'ku to be removed by force, though his efforts were impeded by the Enterprise crew.
Unwilling to wait any longer, Ru'afo decided to commence with the next stage of the operation, without relocating the remaining Ba'ku. When Dougherty objected to this, Ru'afo killed him and deployed the metaphasic collector. Fortunately, Picard was able to stop its activation and trigger the auto-destruct sequence, with help from Ru'afo's second-in-command Gallatin. Soon the Federation Council withdrew their support for the project, with new information from the Enterprise. Some of the Son'a elected to return to the Ba'ku. (Star Trek: Insurrection)
During the Dominion War, the Federation suspected that they were manufacturing large quantities of the Dominion narcotic ketracel-white in the Son'a colonies in the outlying areas near Cardassia and the Bajoran wormhole. In the later days of the war, a recently constructed facility indeed existed at their Devos II outpost. Weyoun diverted a number of Dominion warships to that colony, believing that the Federation knew about it. Damar questioned this, as he felt the Son'a should be able to protect it themselves. (Star Trek: Insurrection, DS9: "Penumbra")
The Son'a equipped their vessels with unpredictable isolytic subspace weapons, in defiance of the Second Khitomer Accord. The Son'a used hand-held disruptor weapons that fired plasma charges. (Star Trek: Insurrection)
A lot of the information in this article, particulary about their early history and culture, was not stated on-screen but instead derives from their file, as studied by Riker and Troi while the Enterprise-E was underway to the Briar Patch.
Among the items sold off on the It's A Wrap! sale and auction on eBay was an unused special effects Son'a face make-up mask. 
According to the Star Trek: Star Charts
- Page 55: The Son'a's homeworld was Son'a Prime. This was a Class K planet governed by the Son'a Solidarity from their capital city Son'a. Son'a Prime was settled circa 2275.
- Page 56: Son'a Prime was located in the Son'a star system. This system's primary was a red giant.