World number eight Tsonga, returning this week from a knee injury that sidelined him for three months after forcing him to retire from his second-round match at Wimbledon in June, recovered from a set down to beat German Florian Mayer 4-6 6-2 6-3 in their semi-final on Saturday.
"I hung on thanks to the crowd's support and also because I knew that Florian Mayer has some endurance problems," Tsonga, who has now beaten the German in their three confrontations, told a courtside interview.
"It will be different against Gilles. I've seen that he's been playing very well," Tsonga said after Simon beat Nicolas Mahut 6-3 7-6 to reach the final without dropping a set on his way.
The 28-year-old top seed, who recently parted ways with coach Roger Rasheed, will seek an 11th ATP Tour title at the indoor tournament where he succeeded in 2011 and 2012.
Simon, seeded two, will also try to clinch an 11th crown after easing past fellow countryman Mahut without conceding a single break chance.
The 16th-ranked Simon had battled with whooping cough, which made him miss the U.S. Open, and arrived in Metz having not won a match since he reached the final at the Eastbourne grasscourt event in June.
He has a 10-4 win-loss record in finals but has never beaten Tsonga on hard courts.
"It's true that I have a good ratio but I lost the last two (in Eastbourne and Bangkok last year). I hope that I will be able to give 100 percent tomorrow," Simon told reporters.
Either Tsonga or Simon will join former world number four Guy Forget as the second most successful Frenchman in the Open era. Only French Open winner Yannick Noah has won more titles - 23 - since 1968.