Sousa finished with four breaks -- two each in the first and third sets -- which offset the one break Melzer managed in each set.
Benneteau ousted second-seeded Stanislas Wawrinka 6-4, 6-3 by converting five of his six break opportunities. He won nearly half -- 29-of-59 -- of the points when Wawrinka served.
Sunday's winner will be a first-time ATP champion. Sousa will be appearing in his first final while Benneteau is 0-8 in title matches. He's been in at least one final each year since 2008 and lost to Juan Martin del Potro in the final in the Netherlands in February.
The Malaysian Open winner will take home $158,000 with second place worth $83,240. Melzer and Wawrinka picked up $45,100 as semifinalists.