1
TV is the most popular media.
TV is the most popular medium.
Medium is singular and media is plural. A medium is a way of communicating information, such as television, radio, the internet or newspapers: ‘Television is an important medium of communication.’
A media outlet is a particular newspaper, television channel, radio station or news website: ‘The story was reported by several media outlets.’
2
The medias are always looking for scandals.
The media are always looking for scandals.
Media is already plural, so do not add -s: ‘The media are reporting the story.’