How to use MeshRenderer.materials

Hello everyone. i just imported a 3d model with two materials from blender and i want to change one of the materials with code and i tried using MeshRenderer.materials[0] = myMaterial but it doesn’t work
can anyone help me?
Thanks!

You can’t change an individual material. Instead, copy them all out, update the one you want then write them all back.

 Material[] allMaterials = gameObject.GetComponent.<Renderer>().materials;
 allMaterials[4] = material6;
 gameObject.GetComponent.<Renderer>().materials = allMaterials;

The documentation says: “If you want to change some materials in it, get the value, change an entry and set materials back.”