There's multiple reasons the mesh isn't deforming as expected. The advice below is based on the blendfile provided.

1. The mesh needs the 'armature' modifier, it currently has no modifiers.
2. The mesh needs weight painting, currently the mesh is unweighted / has no vertex groups.
3. It's a good idea to set the armature as the parent, but in this case that may not work as expected as they have different transformations. To fix that, select both the mesh and the armature and press CTRL+A -> Apply All Transforms. Then you can parent as expected.

I strongly recommend checking out basic rigging tutorials before proceeding (there are a ton of great resources on youtube and other places).

There's multiple reasons the mesh isn't deforming as expected. The advice below is based on the blend file provided.

1. The mesh needs the 'armature' modifier, it currently has no modifiers.
2. The mesh needs weight painting, currently the mesh is unweighted / has no vertex groups.
3. It's a good idea to set the armature as the parent, but in this case that may not work as expected as they have different transformations. To fix that, select both the mesh and the armature and press CTRL+A > Apply All Transforms. Then you can parent as expected.

I strongly recommend checking out basic rigging tutorials before proceeding (there are a ton of great resources on YouTube and other places).