Transformers 2, also known as Transformers: Revenge of the Fallen, can be watched streaming on Amazon Prime Video and Paramount+ (Paramount Plus). It is also available for rent or purchase on platforms like Amazon Video, Apple TV, Fandango at Home, Google TV, YouTube, and others. Additionally, it can be streamed for free on Hoopla where available. However, availability may vary by region. To summarize:

• Streaming subscription services: Amazon Prime Video, Paramount+
• Rent or buy: Amazon Video, Apple TV, Fandango at Home, Google TV, YouTube
• Free streaming with ads: Hoopla (where available)

This provides multiple options to watch the movie depending on your preference for subscription or rental/purchase.