The rapper -- who's one half of Public Enemy -- pulled up to TS's Detroit stop Friday for her ongoing 'Eras' tour, and the dude was ready to prove his love and dedication from the VIP tent ... posing with tons of fans who swung by, and flexing his Swiftie friendship bracelets.

It's pretty sweet ... you see Flav swapping bead bands with young girls, teens and adults alike -- and the guy was totally rocking out during the actual concert too, singing along and dancing.

In fact, it looks like he even had on some Taylor-inspired merch. While TayTay was performing 'Trouble,' -- Flav showed off his T-shirt ... which reads, "I knew she was trouble." Indeed, the guy is a complete and utter Swiftie ... and there's no shame in his game.

Leading up to the big show, Flav appeared to be hyping it up big time ... saying he got his Taylor shirt made just for the event, and even teasing the fact she was coming to town.

While his Taylor fandom might come as a surprise to some, it might've been in our faces the whole time. Earlier this year ... Flav posed with Taylor just a few months ago in March, when she won the Innovator Award during the iHeartRadio Award show ('memba the hoodie 'fit?)

In other words, it sounds like the dude's been in her corner for a while now -- and we're all just learning about it for the first time in public. And while he was sporting Taylor gear, Flav was still on brand ... his clocks and bling were on full display as well, plus his signature hat.

Gotta say ... the Eras tour has proven to be an endless well for news this year. Not only are there storylines surrounding Tay's personal life that feed the beast ... but moments like these cycle in as well and get people fawning over their fave pop star all over again.