“My priority is to get young people into politics, to be a bridge to encourage more of them to participate,” Lim said. “But we also want to prove to the world that democracy works, that even though we have been isolated from the international community, we can make our country a better place.”

Lim’s band, Chthonic, is sometimes known as the “Black Sabbath of Asia” (They last appeared in Hong Kong at the Clockenflap festival in 2014). Although their music is quite different from that of the British pioneers of heavy metal, they somehow managing to blend death metal, or black metal, with the evocative sound of the erhu, a classical Chinese two-stringed instrument. Chthonic prefers to call it “orient metal”.

The band’s name, pronounced “thonic”, comes from a Greek word for the underworld, and Lim’s songs are often inspired by Taiwanese folklore and mythology. But there is politics, too, and anger at the corrupt elite who ruled Taiwan under martial law from 1949 to 1987.

In the video for Supreme Pain for the Tyrant, those martial-law rulers enjoy a debauched party with German Nazis until it is violently broken up by members of the band and the uniformed dictators are killed.

Lim named himself after Freddy Krueger, the razor-wielding serial killer from A Nightmare on Elm Street. But beneath the fierce stage persona, he has never been your typical rock star. Lim and his fellow band members barely drink, and he has been a human-rights activist for two decades, even serving for four years as the youngest chairman of Amnesty International’s Taiwan section.

Hong Kong rappers LMF working hard to promote their lazy ideal with Asian tour before their 20th anniversary

His New Power Party (NPP) grew out of Taiwan’s 2014 “sunflower” student movement, which occupied parliament to protest at closer economic ties with China. From nowhere, the NPP won five parliamentary seats in Taiwan’s 2016 elections, with Lim triumphing in a Taipei district against a well-funded candidate from the then-ruling Kuomintang, whose main line of attack seemed to be mocking Lim’s long hair.

J. Michael Cole, a Taipei-based international affairs analyst, said much of Lim’s appeal lay in his status as an outsider who was not tainted by a political establishment seen by many young people as dysfunctional and anti-democratic. 

“In many ways, his music communicated an anger that was very much present in the hearts of many young Taiwanese,” Cole said.

Lim has been an outspoken advocate for Taiwan’s independence from China, and for Tibetans’ right to self-determination, often waving a Tibetan flag at his concerts and proudly displaying a photo of the Dalai Lama – near one of David Bowie – in his office.

He has also forged links with democratic activists all over Asia at a time when democracy and free speech are under siege from Thailand to the Philippines, Malaysia, Vietnam and Cambodia. He says the people of Taiwan have a special responsibility not to lose hope in the face of constant Chinese pressure.

“We are fully aware of the threats from China, but we need to be optimistic. Otherwise, what will the people of Hong Kong feel, what will Tibetans feel, what will those young people in China feel?” he said. “All the others who suffer in worse conditions, they will still have some hope. They can read the news stories about Taiwan; they can follow in the footsteps of Taiwan; they can still keep fighting.”

At home, the NPP has worked with the 2016 election winners, the Democratic Progressive Party, to pass a “transitional justice” law that aims to remove symbols of the island’s authoritarian past and investigate the purges, executions and abuses committed under it.

They are working towards a law that would make Taiwan the first place in Asia to legalise same-sex marriage, and another to allow refugees, including Tibetans, the right to seek permanent residency. 

On the question of formally declaring independence from China – something that Beijing says it would view as an act of war – Lim the politician is a little more circumspect than Lim the activist rocker.

“Taiwan is an independent country, no doubt. We don’t belong to any other country,” he said. “Of course we want to say we are independent, but this term will be disliked, will lead people to the wrong conclusion.” 

More important, he says, is to build a better Taiwan. “It’s not that we want to fight with China – it’s just our own business, it’s not your business.”

Coachella debut, Marilyn Manson, an English album, neck surgery and the dangers of head banging: Yoshiki of X Japan opens up

Lim the politician is different in other ways from Lim the rock star. He is learning, he says, not just to express his emotions, but also to listen to others. And he is growing up after his wife, Chthonic bassist Doris Yeh, gave birth to their first child, a girl, last year. He also had to cope with the deaths of his father and a close friend.

Lim hasn’t given up music – a long-delayed new album is due this year, but he has played only two live shows since entering parliament.

Lim the singer has often toured the United States, once as part of Ozzfest, the festival organised by former Black Sabbath frontman Ozzy Osbourne. Lim the politician was part of the Taiwanese delegation at US President Donald Trump’s inauguration last year.

He is a big fan of Osbourne but admits to “complicated” feelings about Trump: Lim’s activist friends are not supporters, but he is well aware that the United States is Taiwan’s most important friend and that Trump’s administration is packed with supportive faces.

“In a way, this is the best time for Taiwan to strengthen relations with the United States,” he said. “That’s very important, and it’s my job as a politician.”