What was Caravaggio's black-winged deity of desire? What insights that masterpiece uncovers about the rogue artist

The young lad cries out as his head is forcefully held, a large thumb digging into his cheek as his parent's powerful hand grasps him by the throat. This scene from Abraham's Sacrifice visits the Florentine museum, evoking distress through the artist's harrowing portrayal of the tormented youth from the scriptural account. The painting seems as if Abraham, commanded by the Divine to sacrifice his offspring, could snap his spinal column with a single turn. Yet Abraham's chosen approach involves the metallic grey blade he grips in his remaining palm, prepared to slit Isaac's neck. One definite element remains – whomever posed as the sacrifice for this astonishing piece displayed extraordinary acting skill. Within exists not only dread, surprise and pleading in his shadowed eyes but additionally profound sorrow that a guardian could betray him so completely.

The artist took a familiar biblical tale and transformed it so vibrant and raw that its horrors appeared to unfold directly in front of you

Viewing before the artwork, observers identify this as a actual countenance, an precise depiction of a young model, because the same boy – recognizable by his tousled locks and almost dark eyes – appears in two other works by the master. In every case, that highly emotional visage commands the scene. In John the Baptist, he peers mischievously from the shadows while embracing a lamb. In Amor Vincit Omnia, he smirks with a toughness learned on Rome's alleys, his dark feathery appendages sinister, a naked child creating riot in a well-to-do residence.

Amor Vincit Omnia, currently exhibited at a British museum, represents one of the most discomfiting artworks ever created. Observers feel completely unsettled looking at it. The god of love, whose darts fill people with frequently agonizing longing, is shown as a very real, vividly lit unclothed figure, standing over toppled-over items that include stringed devices, a musical manuscript, metal armour and an builder's T-square. This pile of possessions resembles, deliberately, the geometric and construction gear strewn across the floor in Albrecht Dürer's print Melancholy – save in this case, the gloomy mess is caused by this grinning deity and the turmoil he can unleash.

"Affection sees not with the eyes, but with the soul, / And thus is feathered Love depicted sightless," wrote Shakespeare, shortly prior to this painting was created around 1601. But Caravaggio's Cupid is not unseeing. He gazes directly at you. That countenance – sardonic and rosy-cheeked, staring with bold confidence as he struts naked – is the same one that shrieks in terror in The Sacrifice of Isaac.

When the Italian master created his multiple images of the same distinctive-looking kid in the Eternal City at the start of the 17th century, he was the highly celebrated religious artist in a metropolis ignited by religious renewal. The Sacrifice of Isaac reveals why he was commissioned to decorate sanctuaries: he could adopt a scriptural story that had been depicted numerous occasions previously and make it so new, so unfiltered and visceral that the terror appeared to be happening directly before you.

Yet there was another side to Caravaggio, apparent as quickly as he arrived in the capital in the winter that concluded 1592, as a artist in his early 20s with no teacher or patron in the urban center, only skill and boldness. The majority of the works with which he captured the holy city's attention were anything but holy. That could be the very first resides in the UK's art museum. A young man opens his red mouth in a scream of pain: while stretching out his filthy fingers for a fruit, he has rather been attacked. Boy Bitten By a Lizard is sensuality amid poverty: viewers can see Caravaggio's gloomy room mirrored in the murky liquid of the transparent vase.

The adolescent sports a rose-colored flower in his coiffure – a symbol of the sex commerce in early modern painting. Northern Italian painters such as Tiziano and Palma Vecchio depicted courtesans grasping blooms and, in a painting lost in the second world war but documented through images, Caravaggio represented a renowned female prostitute, clutching a bouquet to her chest. The message of all these botanical indicators is clear: intimacy for sale.

How are we to interpret of Caravaggio's sensual portrayals of boys – and of one adolescent in specific? It is a question that has divided his interpreters since he gained mega-fame in the twentieth century. The complex past truth is that the artist was neither the queer icon that, for example, the filmmaker presented on screen in his twentieth-century movie about the artist, nor so entirely devout that, as certain art scholars improbably claim, his Youth Holding Fruit is in fact a likeness of Jesus.

His early paintings indeed offer overt erotic implications, or including propositions. It's as if the painter, then a destitute youthful artist, aligned with the city's prostitutes, offering himself to survive. In the Florentine gallery, with this thought in mind, observers might look to another initial work, the sixteenth-century masterpiece the god of wine, in which the deity of alcohol stares calmly at you as he begins to undo the dark sash of his robe.

A several years following Bacchus, what could have driven Caravaggio to create Victorious Cupid for the art collector Vincenzo Giustiniani, when he was at last growing almost respectable with prestigious church commissions? This profane pagan deity resurrects the erotic challenges of his initial paintings but in a more powerful, unsettling manner. Fifty years later, its hidden meaning seemed obvious: it was a representation of the painter's companion. A British traveller viewed the painting in about 1649 and was informed its figure has "the body & face of [Caravaggio's|his] own boy or servant that slept with him". The name of this boy was Cecco.

The artist had been deceased for about 40 annums when this story was recorded.