In stars more massive than the sun, the core temperature is hotter, which allows for fusion of more complex elements.
Most of the fusion occurs in the core.
In stars more massive than the sun, fusion continues through Deuterium, Carbon, and finally reaching iron/nickel.
Up to this point, the fusion reaction was endothermic, which means that the energy expended to produce the fusion reaction was exceeded by the energy produced in the reaction.
Fusion past iron is exothermic, and therefore the star will be able to survive by fusing elements heavier than iron.
After the core is almost entirely iron, the star is no longer in the Main Sequence.
So, fusion in stars more massive than the sun continue fusing until the core is almost entirely <em>iron</em>.
