The basic beginning premise is that a young man, who I think was trained in swordsmanship, finds a magical artifact capable of absorbing energy/magic at the cost of his life/vitality. He's able to extend this ability to his weapons. The setting is high fantasy, and the big bad is someone trying to collect all the artifacts, which I believe were all based after the main elements. I think the cover had a medallion on it.
This is potentially Brent Week's Night Angel Trilogy. Significant spoilers ahead.
The main character is known by various names, but for the majority of the books is called Azoth or Kyler Stern. By the end of book one he is in control of a magical artifact known as a Ka'kari.
There are a number of these Ka'kari floating around the story. Each is known by its colour and its effect. Many of these effects are elemental in nature. The red Ka'kari is linked to fire and the blue to water.
Azoth is trained as a Wetboy. Very much a magical assassin, but they don't like being called that. Given the medieval setting this requires some significant sword fighting skills.
The Ka'kari Kyler controls spends a lot of type wrapped around his sword. And the Ka'kari is capable of absorbing magic and bringing Kyler back to life... for a price.
There are several big bads within the series, but the Ka'kari are of interest to all of them.