A sun-sized star will spend most of its lifetime as a:

A sun-sized star will spend most of its lifetime as a main sequence star. It is the stage in a star's life cycle where it maintains as a stable nuclear reaction. The sun in our solar system is a clear example of this. The number of years that these stars would spend at this stage depends largely on the mass of the star. These stars would fuse atoms of hydrogen forming them into helium atoms inside their cores. Fusion reactions are continually happening as days and years pass at this stage. Approximately ninety percent of the stars found in the universe are main sequence stars.