My objects keep falling through

I have objects that are using rigidbody gravity
I want them to fall, but stop when they hit my other object
They just fall through though?

Sounds like you aren’t using colliders. Even if you can see an object, that doesn’t guarantee that it is able to have physics interactions with other objects. In this case, both the Rigidbody object and the object you want it to land on need to have colliders. Colliders specify the shape of an object as treated by the game’s physics. For simple rectangular prisms (3D rectangles), you can use a Box Collider. Other colliders include the Capsule Collider, and the Mesh Collider. The Mesh Collider is special in that it shapes itself to match a mesh that the object is using. Terrain objects can also use the specialized Terrain Collider which perfectly matches the Terrain object it is attached to. Once both your Rigidbody object and the object you want it to land on have colliders attached to them, you will find that they no longer pass through each other.