This common misconception is possibly the most absurd concern.
It’s the equivalent of wondering if revving your WagonR too hard will turn it into a Porsche.
Hard truth
Muscle is made out of very different looking cells than fat.
The fundamental parts that make up a muscle cell be it actin, myosin, titin among many components are very different from the giant globule of fat inside a fat cell.
Fatty detail
Among fat cells, the brown and white variants look quite different. One has several droplets (brown). The other has one large droplet (white). The brown has more mitochondria than the white.
Muscles have many more mitochondria and different kinds of protein in them.
Simply put, your body does not have a mechanism to rearrange fat cells into muscle cells if you do a few squats or bicep curls.
There needs to exist conditions for the fat cells to be mobilised and used as energy. The conditions are usually an energy deficit or a tonne of activity.
There needs to exist conditions for muscles to grow The exercise, nutrients, rest etc to facilitate said growth.
But under no circumstance, do fat cells 'transform' into muscle.
Takeaway
The effort to grow muscle is entirely underrated by the general population.
Not to mention, most people wildly overestimate how lean they are. And they underestimate their body fat levels to a gargantuan degree.
This is a problem given the overwhelming evidence that carrying too much body fat is just counterproductive for health and quality of life.
Body composition is not about not about the photoshop lobby, vanity or about how your body looks. It’s about how it works. Or rather how much better it can work sans a few percentage points of fat.