♪ this is "nightline." >> tonight, bts exclusive. the world's hottest boy band getting permission to dance. ♪ we don't need permission to dance ♪ >> at the united nations on a mission with south korea's president, moon jae-in. talking climate action and covid. >> how does bts become sort of a tool of global diplomacy? >> sharing moves with the head of state and juju chang. >> this is breaking. >> revealing how they've coped with pandemic isolation. and the moment that got so much attention on social media. "nightline" will be right back. tums vs. mozzarella stick

when heartburn hits, fight back fast with tums chewy bites. fast heartburn relief in every bite. crunchy outside, chewy inside. ♪ tums, tums, tums, tums ♪ tums chewy bites ♪ we'll bring the pieces that inspire. you bring a desire to play and discover. together, we'll create a style that is trademark 'you'.

♪ thanks for joining us. they are, simply put, the hottest boy band on the planet. with 23 guinness world records, from sales to streaming to social media. but the seven superstars of bts and their army of fans are now being called into service after south korea's president appointed them special envoys,

hoping to make a difference for their generation. ♪ >> reporter: only these seven superstars can pull off a feat like this. bts, the korean powerhouse, flew halfway around the world to sing and dance through the night in the dignified halls of the united nations, to their record-breaking hit "permission to dance." ♪ we don't need permission to dance ♪ >> it's a lot of jet lag and sleep deprivation at the same time. all-nighter, as we call it in the united states. >> reporter: the precision choreography and marathon performance was perhaps the easiest part of their whirlwind trip. this week they took the stage to speak to the world's most powerful dignitaries. their new role, korean president

moon jae-in's special presidential envoys for future generations and culture. this partnership between the world's biggest boy band and a head of state perhaps an unlikely pairing. the goal, to bridge the generation gap and tackle some of the world's most daunting crises, like poverty and the pandemic.

>> reporter: the seven members together rake in billions of dollars of revenue each year, with five number one albums. they're the most streamed group on spotify all-time. right now they average 20 million views on youtube every day. ♪ their summer smash hit "butter" with a record-breaking debut at number one on billboard's global 200 chart. ♪ get it let it grow ♪ >> reporter: their international fame brought unprecedented live views for the u.n. >> a million people tuned in to watch live, which doesn't usually happen at a u.n. proceeding. how does bts become sort of a tool of global diplomacy?

♪ >> reporter: to prepare for their u.n. mission, bts posted #yourstories, to share what young people are most worried about. >> what are you trying to say to your fans? to be able to effect some change in combating climate crisis?

>> reporter: bts is fully aware of the responsibility that comes with their new title. you guys are an all-male band. let's face it, korea historically has been a very male-dominated culture. yet here at the u.n., one of the core values in sustainable development is educating women and having gender equality. you have a lot of female fans. what would you say to them about gender equality and working towards that?

>> reporter: it's not just gender equity. bts has leaned into other social justice issues, donating $1 million to black ives matter last year, matched by their fans. and now they're encouraging all fans to get vaccinated.

>> reporter: with that in mind, korean president moon has pledged $200 million to covax, the u.n.'s vaccine equity program. >> reporter: only 43% of koreans are fully vaccinated, compared to 55% here in the u.s.

>> reporter: but the pandemic and even climate action is merely a backdrop to renewed tensions on the korean peninsula. just last week, north korea testing and firing several missiles, reigniting fears of a destabilized asia-pacific region. what would you say to president biden about these developments, and how do we ease these tensions? >> reporter: president moon's term ends in a matter of months, and while the north korean summit which he helped broker

was history-making, so too were cultural milestones. like "parasite," the first korean film to win best picture at the oscars. while in new york, bts joined the korean first lady to donate modern korean art to the famed metropolitan museum. >> global power isn't just about military might or even economic might. in many ways it's about cultural influences, cultural exports. how are you trying to harness the korean cultural export to get people to pay attention to these global issues?

>> secretary-general ban ki-moon famously danced with psi gangnam style. will you do a permission to dance with bts? this is pretty good. even i can do this. what is this? it's a group dance, it's the korean in us. coming up, the seven superstars share their own struggles during the pandemic.

people everywhere living with type 2 diabetes are waking up to what's possible with rybelsus®. ♪ you are my sunshine ♪ ♪ my only sunshine... ♪ rybelsus® works differently than any other diabetes pill to lower blood sugar in all 3 of these ways... increases insulin when you need it... decreases sugar... and slows food.

the majority of people taking rybelsus® lowered their blood sugar and reached an a1c of less than 7. people taking rybelsus® lost up to 8 pounds. rybelsus® isn't for peopl with type 1 diabetes. don't take rybelsus® if you or your family ever had medullary thyroid cancer, or have multiple endocrin neoplasia syndrome type 2 or if allergic to it. stop rybelsus® and get medical help right away if you get a lump or swelling in your neck, severe stomach pain, or an allergic reaction. serious side effects may include pancreatitis. tell your provider about vision problems or changes taking rybelsus® with a sulfonylurea or insulin increases low blood sugar risk. side effects like nausea, vomiting, and diarrhea may lead to dehydration, which may worsen kidney problems. wake up to what's possibl with rybelsus®. ♪ please don't take my sunshine away ♪ you may pay as little as $10 per prescription.

ask your healthcare provider about rybelsus® today.

kids love visiting kidifornia. but parents like it to, like a lot. they go bonkers. (wuaahh) totally boom it's an adventure. (sound of playing) you know ,you have to keep an eye on them. you got to let them explore and figure things out for themselves. so hurry up (screams)

they're not gonna stay this way forever. kick off your kidifornia vacation at visitcalifornia.com ♪ ♪ throughout the pandemic, bts has performed three blockbuster virtual concerts. got inducted into the guinness world records hall of fame. earned their first grammy nomination. and won seven vmas. >> we love you and we miss you. >> thank you so much! >> leading a seemingly

illustrious life in lockdown. but bts, all in their 20s, say privately they too struggle with the effects of covid isolation, referred to as "the corona blues" in korea. it's been a year and a half since the group performed live in front of fans. just last month, they once again postponed their long-awaited global tour.

>> even j-hope, known for his bubbly and optimistic personality, says he's had a rough time.

>> mental health struggles and depression are often taboo products in korea, but runner suga has been open about his bouts with depression, ocd, and other problems even writing about it in his solo track "the last." i know you've talked about your struggles with mental health and depression before. i wonder if you'd like to give encouraging messages and what, if anything, you've learned throughout this pandemic.

>> and on the other side, they're hoping to see and connect with the army once again.

up next, the big reveal. what did i say to rm? the internet wants to know. you'll find out. (vo) for over 50 years purina cat chow has been helping cats feel at home. with trusted nutrition, no wonder it's the number one dry cat food in america. come home to cat chow. i've got moderate to severe plaque psoriasis. now, there's skyrizi. ♪ things are getting clearer ♪

♪ i feel free ♪ ♪ to bare my skin, yeah, that's all me ♪ ♪ nothing and me go hand in hand ♪ ♪ nothing on my skin, that's my new plan ♪ ♪ nothing is everything ♪ achieve clearer skin with skyrizi. 3 out of 4 people achieved 90% clearer skin at 4 months. of those, nearly 9 out of 10 sustained it through 1 year. and skyrizi is 4 doses a year, after 2 starter doses. ♪ i see nothing in a different way ♪ ♪ it's my moment so i just gotta say ♪ ♪ nothing is everything ♪ skyrizi may increase your risk of infections and lower your ability to fight them. before treatment, your doctor should check you for infections and tuberculosis. tell your doctor if you have an infection or symptoms... such as fevers, sweats, chills, muscle aches, or coughs... or if you plan to or recently received a vaccine. ♪ nothing is everything ♪ talk to your dermatologist about skyrizi. learn how abbvie could help you save.

♪ finally tonight, a mystery revealed. i'm not used to blowing up on social media, so it was a bit of a surprise when my greeting with rm from bts did just that. so many on social media speculating and coming up with fan theories. what did i say? it really wasn't that big a deal. i simply said this. >> you were terrific. >> referring to the metropolitan museum event the day before. rm's bashful reaction? really, modesty. mystery solved.

that's "nightline." you can watch our full episodes on hulu. see you here same time next week. thanks for staying up with us. good night, america.