Trademarks are short phrases, or symbols, or logos, or shapes, or colors, etc., that companies create to distinguish their product or service.
1. Prevent Consumer Confusion
The mark identifies the source of the product.
Trademark infringement occurs if you confuse the consumer as to the source of the product.
2. Prevent Unfair Competition
Same logic as copyright.
You can't benefit from another's work without permission.
Trademarks Infringement
Infringement: using someone else's mark to promote or sell a similar product.
Trademark dilution: showing a product in the film in a way that would confuse the consumer with another product or make the mark generic.
Trademark tarnishment (or defamation): impugning or showing the product as defective.
Tarnish the brand: you are using the product in the manner it was not intended. Disparage or harm its reputation. (defamation of false)
Product Placement
An advertising technique used by companies to subtly promote their products.
Names and Titles
Most names & titles of movies are not trademarked (a stand-alone movie cannot be trademarked), unless:
It has a lasting presence in the marketplace (you are going to use it over a long period of time).
It is a series of works.
You are going to manufacture merchandise.
Titles are protected through the MPAA (by contract).
Members agree not to use a title that is confusingly similar to another title, and agree to handle any disputes that arise through arbitration.
This system is enforced via contractual rights.
Independent producers may opt in.
You will have to prove you have the right to use a title (to get insurance and distribution).
A common way is to get a Title Report.
Unfair Competition
However be aware of unfair competition laws:
Palming off (or passing off): using a name or title of someone else’s product in order to commercialize your product.
The law of passing off prevents one from holding out his goods or services (film) as having some association or connection with another when this is not true.