Photons, as massless particles, do not directly contribute to the curvature of spacetime through their mass. However, according to Einstein's theory of general relativity, energy and momentum, including that carried by photons, do influence the curvature of spacetime. This means that while photons themselves do not warp spacetime due to their mass, they can still have an effect on the geometry of the universe.
In general relativity, mass and energy are related through the famous equation E=mc². Photons have energy due to their motion and their interaction with matter. When a photon passes through a gravitational field, its energy and momentum interact with the curvature of spacetime, causing a gravitational effect.
A well-known example is the gravitational bending of light. When light passes near a massive object, such as a star or a black hole, the path of the light is curved due to the gravitational field of that object. This phenomenon was famously confirmed during the 1919 solar eclipse when the bending of starlight by the Sun's gravity was observed.
So, while photons themselves do not possess mass, they can still indirectly influence the curvature of spacetime through their energy and momentum, resulting in observable gravitational effects such as the bending of light.