How can I resolve the iMac Bluetooth connection error with iPhone 16?

Betto Teixeira wrote:

In my iPhone 16 (Settings> Bluetooth > OTHER DEVICES > "iMac"), trying to connect, the error message is presented (Pairing Unsuccessful "iMac" is not supported).

It is weird because the Air Drop works well.

As KiltedTim correctly points out, iPhone, nor iPad will pair with a Mac in the traditional Bluetooth pairing way. There is no need for them to pair. Instead, Apple uses Continuity, which you can learn about here --> Continuity features and requirements for Apple devices - Apple Support

Macs and iPhones do not support Bluetooth pairing with each other. They work together in other ways including

• Synchronization through iCloud, shared e-mail accounts, and third-party cloud services
• Continuity features (Continuity features and requirements for Apple devices - Apple Support)
• Shared access to subscription services such as iCloud+, Apple Music, Apple TV, and Apple Arcade
• Manual synchronization (e.g., of music purchased on CD) to an iPhone from a Mac

That's correct. You can not pair an iPhone or iPad with a computer or another iOS or iPadOS based device.

Traditional pairing is not necessary.

What are you hoping to accomplish by doing that?