In many Sasuke - Sakura - Gaara fanfictions, Sasuke saving Sakura from Gaara can be a really exciting plot. It often shows Sasuke's strength and his hidden feelings for Sakura. Maybe he uses his Sharingan to outwit Gaara's sand attacks and rescue Sakura just in time.
Well, in many such fanfictions, Gaara might use his sand powers. He could sense Naruto is in danger through his connection to the sand or his own instincts. Then, he'd quickly move in, using his sand to shield Naruto from any attacks by the Akatsuki members, like blocking their jutsu with his powerful sand barriers.
They could be just ordinary wizards who happened to cross paths with Harry Potter. Maybe they have a special interest in orphans or in Harry specifically because of his unique situation as the boy who survived Voldemort's attack.
One common theme is the display of Sasuke's heroism. He is often depicted as the strong and capable ninja who can overcome Gaara's power to save Sakura.
One reason is their friendship. Naruto was one of the first people to see Gaara as a person, not a monster. So, Gaara would feel indebted to Naruto and be willing to risk his life. Another reason could be for the sake of the ninja world. Naruto is often seen as a key figure in maintaining peace, and Gaara, as a responsible leader, would understand the importance of saving him.
Another theme is mutual respect. They both have unique skills. Gaara with his sand control and Lee with his taijutsu. Fanfics often show how they come to respect each other's abilities. In some, they even learn from each other, like Lee teaching Gaara about the value of hard work and Gaara showing Lee how to be more in tune with his inner self.
Another theme is personal growth. Lee can grow in his understanding of those with a darker past like Gaara, and Gaara can learn to open up more because of Lee's positive influence. In many 'lee x gaara fanfic', this mutual growth is beautifully depicted through various plotlines, like when they face a common enemy and have to rely on each other not just physically but also emotionally, which leads to them becoming better versions of themselves.
The theme of redemption also appears sometimes. Gaara's past actions and his journey to redemption can be intertwined with his relationship with Lee. Lee's positive influence on Gaara and vice versa, in terms of helping each other grow and become better shinobi, is a common thread in these fanfictions.