To install Metasploit on Debian 12, you can follow these steps:

1. Update the package lists and upgrade the system:

   sudo apt update
   sudo apt upgrade
   

2. Install the required dependencies:

   sudo apt install curl gnupg2
   

3. Import the Metasploit repository GPG key:

   curl https://apt.metasploit.com/metasploit-framework.gpg.key | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/metasploit-framework.gpg
   

4. Add the Metasploit repository to the sources list:

   echo "deb [arch=amd64] https://apt.metasploit.com/ bookworm main" | sudo tee /etc/apt/sources.list.d/metasploit-framework.list
   

5. Update the package lists again:

   sudo apt update
   

6. Install Metasploit:

   sudo apt install metasploit-framework
   

7. After the installation is complete, you can start Metasploit by running:

   msfconsole
   

Please note that Metasploit is a powerful tool and should only be used for ethical purposes, such as penetration testing on authorized systems.