Warfire by Sam Burns

Ares has been an outcast for millennia. He never fit amongst the perfect golden gods of Olympus, and wandering the land from battle to battle has taken its toll. Yet when the titans return, he musters for one last battle, knowing it could be his last.
Adrian Wagner is a monster. After a fatal crash a decade ago, he rose as a vampire, but dragons? Well, those are something else. When an attack on the Hunt building imbues him with uncontrollable fire, he not only has to contend with the dragon inside him but also develops a strong bond to the ancient, terrifying, leather-clad warrior who once rode over battlefields on the back of the mighty wyrm now occupying Adrian’s body.
Only Ares isn’t what Adrian expected, and unraveling the layers of the misunderstood god proves the most worthwhile effort in Adrian’s short immortality. Too bad they met in the middle of a war that might kill them both.