Jeremy Wallach, an ethnomusicologist at the Bowling Green State University in Ohio and author of Modern Noise, Fluid Genres: Popular Music in Indonesia, 1997-2001, says the metal subculture in Indonesia has grown rapidly since the 1990s. The underground metal scene has often helped focus resistance there; it is partly responsible for toppling the autocratic Suharto regime in 1998 and helping to foster a new democratic society in its place.

Since then, the nation has continued to produce metal goliaths, pummelling heavy sounds into the ears of frenzied crowds in and out of the country and winning global metal awards. The country also hosts the largest annual metal festival in Southeast Asia, Hammersonic, which draws more than 30,000 metalheads.

Even the Indonesian president himself is a self-proclaimed heavy metal devotee. Joko Widodo is often seen sporting a metal band T-shirt and leather jacket, while playfully flashing the devil horns sign when being photographed. He has told the media that he is a big fan of Lamb of God, Metallica and Napalm Death. Randy Blythe, the frontman of Lamb of God, calls Widodo “the world’s first heavy metal president”.

So how did a genre with the reputation of being the devil’s music became so widely celebrated in a nation where 87 per cent of its population is Muslim? The answer, it seems, lies in Indonesia’s diverse attitude toward religion and spirituality.

Yuka Narendra, a metal studies scholar and researcher from Matana University in Tangerang city, believes the phenomenon exists due to a culturally integrated Islam that can only be found in Indonesia.

In Indonesia, he says, 80 per cent of metalheads are Muslims, “but in comparison with Islam in the Middle East, our Islam is more fluid. For centuries, cultural practices have intermingled within the Islamic domain, and even the early Islamic teachings in Indonesia have involved traditional music, songs and songwriting.”

This has created a more relaxed and adaptive version of Islam in Indonesia, with a society that is more open towards cultural expression – including heavy metal.

“Take a look at Hammersonic,” Narendra says. “It’s a metal festival with prayer breaks. You wouldn’t find that in any other part of the world.”

It is perhaps not surprising that this blending of cultural identities can be found all across Indonesia. Take the case of 16-year-old Firda Kurnia from Garut, a small town about five hours away from Indonesia’s capital city of Jakarta.

Kurnia describes herself as a devout Muslim. She wears a hijab, prays five times a day, and even gives Koran readings at an Islamic school in her local neighbourhood. For Kurnia, Islam is a part of her identity, and her faith is ever present in her daily life.

Yet between her daily routine of school and prayers, Kurnia travels from one gig to another, banging her head to aggressive heavy metal beats and pushing metalheads into the mosh pit as the lead singer and guitarist of Voice of Baceprot (VoB).

VoB is a Garut-based heavy metal band made up of three hijab-clad girls in their teens. The band has been around for three years, but they became a viral sensation in April after a clip of them thrashing away to a heavy metal track made the rounds on the internet.

Kurnia believes her musical path does not conflict with her faith. “I play metal music as a hobby, but my religion is my personal relationship with God. My lyrics are ‘clean’; we sing about our restlessness, about the state of our Mother Earth, about the education system in Indonesia,” she says.

“Even when we’re planning to do a cover song, the whole band sits down and tries to dissect the lyrics and the meanings behind the song. If we find any words that are offensive or against our beliefs, we’ll try to get creative and find a substitute.”

She admits that being the frontwoman of a hijab-wearing metal band has not always been easy and they have faced criticism since the band’s popularity skyrocketed.

“They told me that I should take off my hijab, that metal is the music of the devil, and that it’s blasphemous to wear a hijab while playing metal music,” Kurnia says, pointing to comments on social media.

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But Kurnia doesn’t see it that way. “Wearing a hijab is part of my identity as a Muslim woman, while metal is a musical genre which I happen to feel very passionate about. We don’t consider ourselves an ‘Islamic metal band’. We are just three teenage Muslims in a band, who play heavy metal music.”

She believes that the recognition her band has received has made it easier for other metal-loving hijabis to step into the light.

“I’m sure they have always been around, but they might have felt uneasy showing up at gigs because they didn’t think that it was their ‘scene’. But now that we’ve been widely covered in national media, I’m beginning to see more and more girls in hijabs at metal shows. They know that they can love and enjoy the music while at the same time feel comfortable with expressing their Islamic identity.”

In Indonesia, Islam is not the only religion being released into the metal vortex. About 400km away from Garut in Surakarta, the hometown of President Widodo, Stephanus Adjie is known for blending elements of Catholic doctrine, Islamic verses and Javanese rituals into his music.

The frontman of Down For Life, one of Surakarta’s most respected heavy metal bands, Adjie was born, raised and educated as a Catholic, but all of his bandmates are Muslims.

Adjie gives an example of the use of different religious symbology in the band’s music. “In one of our songs, Liturgi Penyesatan (‘Liturgical Apostasy’), Koranic verses are used as the intro, and the Lord’s Prayer as the outro.”

But Down For Life don’t consider themselves a religious band. “We’re very spiritual,” Adjie says. “Catholic doctrines, Islamic verses – these are symbols of spirituality that are inherent within our culture in Indonesia. Our music makes way for spirituality to manifest itself.”

Adjie thinks it is this spiritual catharsis that has allowed the music to become embraced in Indonesia. “In every facet of life, Indonesians are very spiritual. Our local metal scene is no different. Picture thousands of metalheads with their black T-shirts, often with sacrilegious imagery, doing Islamic prayers in between headbanging and mosh pits. Yes, the music is from the West, but when it made its way here, we tweaked it so that it fits our culture.”

This cultural malleability has given birth to a new metal subculture in Indonesia. With the rise of Islamic conservatism in Indonesia came the arrival of “Metal Satu Jari”, or “one-fingered metal”, which replaces the two-fingered sign of the horns with one single raised index finger to symbolise one god.

Metal studies scholar Narendra says this movement gained momentum in 2010 and most of these bands are veterans who traded satanic codes with Islamic symbols.

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He explains that as a counter movement, the government launched a programme titled “Metal Untuk Semua”, or “metal for everyone”. This aims to promote a more inclusive scene that lets everyone from any religion, ethnicity, or race headbang to heavy metal.

“Indonesia’s heavy metal music scene is a melting pot of cultural identities, and religion and spiritualism are one of main ways the Indonesian identity is being constructed,” Narendra says. “The music itself, essentially, will always be the music of resistance and resilience.”