The former First Couple took the stage Friday at the Martha's Vineyard African-American Film Festival -- where they said a few words before a screening of their Netflix doc, "Descendant." As you can see, they were very warmly received ... the crowd seemed shocked they showed.

Eventually, they each delivered remarks ... BO talked about the power of telling stories -- Black stories, specifically -- and praised the festival organizers for allowing African-Americans to do just that through their event.

He said, "[I]t's one of the powers of this festival, and the work that the Rances have done is to lift up stories that too often have been lost in the flow of time. Because we believe that everybody's stories matter. Everybody's got a sacred story that motivates us, moves us. It's not just a matter of nostalgia, it powers us into the present and the future."

Michelle hit that point home by noting the older generation should be encouraging their youth to actually talk to their grandparents and great-grandparents -- and take in their history while they still can. She also took some playful shots at IG and TikTok trends in the process.

The audience was feeling what she was saying ... as they were audibly agreed throughout. Pretty cool to see 'em here -- even though they're low-key in MV quite a bit. Of course, they have a summer home there (a mansion actually), so they're no strangers to the area.

BTW, as for what their Netflix-backed doc is actually about ... "Descendant" covers a small Alabama community that has descendants from the Clotilda, one of the last slave ships to have sent over Africans to the States just as it was being outlawed nationally.