Maturity is an often derided concept in a youth-facing art form. But when Simmer, a song about repressed feminist rage buoyed by creepy electronics – the lead track from Hayley Williams’s debut solo album – was released in January, it signalled an intriguing sea change in an artist previously known as a bouncy, flame-haired emo cheerleader.

The story of how Hayley Williams, now 31, went from leading angsty emo shoutalongs in the Tennessee pop-punk band Paramore to releasing these startling songs about rage, femininity and suicidal thoughts is one of the knottier yarns in contemporary American guitar music. Her trio-of-EPs album is now complete, with the final EP – and a physical album uniting all three – released last Friday.

Petals for Armor is not about Williams’s time with Paramore, per se, but her recovery from a band she had been in since her teens, an outfit run on equal parts camaraderie and acrimony, tinged by God and latterday poptimist repositioning.

From teenage beginnings, Paramore grew into one of the genre’s premier arena-fillers, via endless Vans-sponsored touring festivals and umpteen packets of bright hair dye. Echoing Blondie in the early 80s, Williams would scrawl “Paramore Is A Band” on her T-shirt (she was signed as a solo act, but insisted on forming a band). When Williams and her good buddy Taylor Swift first met, at a Grammys party in 2008, Williams was arguably nearly as big in her own sphere as her Nashville peer was in hers.

Certainly, the Paramore singer held an early lead on drama as fuel for songs. In just one minor subplot, Paramore’s bassist left, returned and eventually left again, a lawsuit in his wake. In 2010, original guitarist Josh Farro left the band with his drummer brother, Zac, calling Paramore, not without some justification, “a manufactured product”, and accusing Williams, less quantifiably, of insufficient godliness. The fact that Farro and Williams had been in a semi-unrecognised relationship – see Paramore’s 2009’s Brand New Eyes LP – just added to the feeling of watching a soap opera with gnarlier chord play.

By the time Paramore made 2017’s redefining After Laughter, Zac Farro was back; Williams had divorced her partner of nearly a decade; Paramore’s second guitarist, Taylor York, was playing lead and producing; and the band had pivoted away from moshpits towards a zesty, early 80s-indebted funk-pop that barely masked some seriously bleak lyrics.

Williams’s label, Atlantic, played a very long game because now, after After Laughter, it finally has a Hayley Williams solo album, Petals for Armor, whose theme is strength through vulnerability.

Williams’s output has grown up immeasurably. Sudden Desire is a borderline R&B song about female lust, a theme that contrasts markedly with Paramore’s careful messaging. An overarching concern on Petals… is how Williams constructs a workable new femininity free from her old tomboy identity in Paramore. The blooming metaphor is, as a result, slightly overplayed throughout. But songs such as Roses/Lotus/Violet/Iris, with its theme of female solidarity – emphasised by Phoebe Bridgers, Julien Baker and Lucy Dacus (AKA Boygenius) on backing vocals – just avoids gilding that lily too much.

A personal and artistic reboot, Petals for Armor processes, post-therapy, everything Williams has been through – Paramore, the trauma laid down in Williams’s childhood, when her mother had to escape an abusive partner, and Williams’s own various relationship breakdowns. The black squares that adorn Williams’s hand on her album’s artwork hide the tattooed-over initials of her former husband.

All these factors sent Williams close to the edge. In an Apple Music interview last February, she told Zane Lowe that only the thought of her dog waiting for her in vain quelled her suicidal thoughts. A tremendous song such as Leave It Alone, which mixes acoustic guitar with strings, treats these dark matters gently, with Williams imagining new uses for “the noose that she made” (“turn it into a fire escape”).

If the floral theme can feel a little much, the experimentation sometimes struggles to hit the right note. Watch Me While I Bloom starts as a surprise, Björk-like explosion of self-love and slithering electronics and develops into Janet Jackson funk. It’s not wrong, but on those funkier occasions when Williams turns to face the mainstream, she loses her individuality. Pure Lover is one tune where the hard-won wisdom of her lyrics – “If I want pure love, must stop acting so tough” – is lost in a swirl of textbook funk-pop. The refusal to sit with any genre longer than a few bars confuses just as often as it impresses.

Most courageously, however, this is not the sort of Damascene pop conversion where Williams dallies with all the A-list producers du jour, as Gwen Stefani, a trailblazer of sorts, did when her first band, No Doubt, ended. Although there are a couple of low-key co-writes, Williams and York remain the organising creatives, and Williams sounds both free and in control.

The unfettered glee with which these former pop-punk lifers go about renewal is striking, never more so than on Cinnamon. Here, upfront percussion, Williams’s vocals and paranoid electronics bounce off one another on a song about the spooky house she moved into, alone, after her divorce. The song’s upshot provides a useful precis of Petals: Williams has grown to love her solitude.

In the UK and Ireland, Samaritans can be contacted on 116 123 or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at befrienders.org