Gamma "particles" are electromagnetic radiation, waves, which accompany the emission of alpha and beta particles. Radiation can also be considered as a particle according to De Broglie's theory which states that all waves have an associated particle, light waves have associated photons.

The characteristics of g waves are:

They would have no mass at rest, they move at the speed of light.
They have no electric charge, so they are not deflected by electric or magnetic fields.
They have little ionizing power, although they are very penetrating. The gamma rays from Ra can penetrate up to 15 cm of steel.
They are waves like light but have even more energy than X rays.
A radioactive compound which is absorbed by a gland and emits gamma radiation allows us to study this gland by obtaining a plate, like a photographic one, with the emitted radiation. The technique is called gammagraphy.
Activity: Work with this visual to see what type of material and what thickness a sheet of metal should have to stop this radiation.