Anchoring metal sculptures in sandy or unstable soil can be challenging, but with the right techniques, you can ensure stability and durability. Here are the best practices to follow:

1. Deep Foundation: Dig deep into the soil to reach more stable layers. A deeper foundation provides better support and prevents shifting.

2. Concrete Footings: Use concrete footings or piers to create a solid base. Pour concrete into the hole and embed the sculpture's anchor bolts or rebar for added strength.

3. Helical Anchors: Consider helical anchors or screw piles, which are ideal for sandy soil. These twist into the ground and provide excellent grip.

4. Weight Distribution: Spread the weight evenly by using a wide base or platform. This reduces the risk of the sculpture sinking or tilting over time.

5. Drainage Considerations: Ensure proper drainage around the sculpture to prevent water accumulation, which can weaken the soil further.

6. Regular Maintenance: Inspect the sculpture and its foundation periodically, especially after heavy rains or storms, to address any signs of instability.

By following these best practices, you can securely anchor metal sculptures in sandy or unstable soil, ensuring they remain stable and visually striking for years to come.