The King presented K-pop band Blackpink with honorary MBEs a day after hailing them as environmental champions.
Charles handed medals to South Korean megastars Jennie Kim, Jisoo Kim, Lisa Manobal and Rose Park at Buckingham Palace.
They were joined by the country's President Yoon Suk Yeol and First Lady Kim Keon Hee during their state visit to the UK.
The King told the band he was "so glad" to present them with the MBEs adding he hoped to see them "perform live at some point".
Jennie told the King that receiving the MBE was "the most honourable thing for us".
The biggest girl group in South Korea amassed millions of views on their climate videos during the COP26 in Glasgow two years ago after being appointed as one of the summit's advocates.
One of their appeals features the band members speaking in English, Thai and Chinese as they called for global leaders to take climate action and "save our planet".
After the presentation, Charles discussed the band's recent tour and joked to the group:
"The great thing is that you're still talking to each other after all these years of working together."
Blackpink became the first Korean band to headline a major UK festival, BST Hyde Park, during the summer.
One of the band's most popular songs Ddu-Du, Ddu-Du - with more than 2 billion hits on YouTube - was played during the guard change.
Viral K-pop song, Gangnam Style, by Psy and the Korean folk song, Arirang, were also played before the investiture.
The musical tribute to South Korea comes a day after the King praised Blackpink during his state banquet address.
He said:
"I applaud Jennie, Jisoo, Lisa and Rose, better known collectively as Blackpink, for their role in bringing the message of environmental sustainability to a global audience as ambassadors for the UK's presidency of COP26, and later as advocates for the UN sustainable development goals.
"I can only admire how they can prioritise these vital issues, as well as being global superstars. Sadly, when I was in Seoul all those years ago, I am not sure I developed much of what might be called the Gangnam Style!"
K-pop, short for Korean popular music, includes styles and genres from around the world, such as hip hop, rock and R&B, on top of its traditional Korean music roots.
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