This tool named Blockbench is a good tool for 3D modeling if you like the Minecraft game style.
You can use it online or download it for desktop.
The target platforms are: 
- Minecraft: Java Edition
 - Minecraft: Bedrock Edition
 - Hytale
 - Rendering / Game Engine
 
This video shows the basics of modeling in Blockbench to create custom models for Minecraft bedrock that you can put in Minecraft maps and worlds.