How is the idea of lust expressed in The Picture of Dorian Gray by Oscar Wilde?

This book takes place in late-nineteenth-century London, a time and place characterized by extravagance and artistry flying in the face of traditional, conservative values. It comes as little surprise that lust was one such indulgence on the rise, yet still mired in controversy.
Lord Henry perhaps articulates this idea best in chapter 2, when he says:

"I believe that if one man were to live out his life fully and completely, were to give form to every feeling, expression to every thought, reality to every dream—I believe that the world would gain such a fresh impulse of joy that we would forget all the maladies of mediaevalism, and return to the Hellenic ideal—to something finer, richer than the Hellenic ideal, it may be. But the bravest man amongst us is afraid of himself. The mutilation of the savage has its tragic survival in the self-denial that mars our lives. We are punished for our refusals. Every impulse that we strive to strangle broods in the mind and poisons us. The body sins once, and has done with its sin, for action is a mode of purification. Nothing remains then but the recollection of a pleasure, or the luxury of a regret. The only way to get rid of a temptation is to yield to it. Resist it, and your soul grows sick with longing for the things it has forbidden to itself, with desire for what its monstrous laws have made monstrous and unlawful."

These ideas are continually developed and tested throughout the book. In regard to lust, the modern attitude to is to allow it to take shape, to "give form to every feeling." Yet, as Lord Henry points out, people find it difficult to succumb to even their strongest impulses (sexual or otherwise) because "the bravest man amongst us is afraid of himself." The Picture of Dorian Gray is teeming with vexed desires; characters lust after one another, ideas, and vain ambitions and yet are scared of those same cravings.
Lord Henry himself is married, yet admits that he and his wife cheat on one another, asserting that all marriage is a disappointment to both parties. Such married couples in this book value sexual satiation and excitement over fidelity. There are also strong overtones of homosexual affection and desire between Dorian Gray, Basil, and Lord Henry. As homosexuality was deemed completely unacceptable in this book's setting, the three men would naturally feel complicated about their lust for one another, admiring one another's physical and personal charms, essentially flirting, while never being able to indulge in actual sex or romance. Basil's idolatry of Dorian especially reads as unrequited lust or love. Sybil Vane and Dorian Gray desire one another, but had such profound misconceptions about one another's character and values, the whole affair ended not only in unfulfilled longings, but tragedy.
From one point of view, succumbing to lust is a kind of freedom, and on the other hand, that freedom is so difficult to pursue it may end in disaster and not be worth it from the start. Like most other topics Wilde addresses, there is no definite answer as to how we should regard lust and longing. There are merely two perpetually clashing perspectives on the question, which cause havoc in the lives of the characters.