Even though this is featured in the Gameplay Series Part 2 video, I thought it deserved its own thread. As featured in the video, Mass Effect: Andromeda will have an M rating due to the following reasons: blood, nudity, strong language, strong sexual content, and violence.
"Nudity" and "strong sexual content" are of particular note, such features being largely reduced or removed since Mass Effect (1) showed off some butt and side boob.
Now, if you happen to not particularly know, the M rating means the game is made for "mature" audiences. Many retailers restrict the sales of such games to individuals 17 years old or older, as the content can be "too much" for younger individuals, and your area may even have laws restricting these sales.
If you're younger and your retailer does restrict sales, I recommend informing the person purchasing your copy ahead of time, just because the whole "naked aliens" talk with them might be a bit awkward after the fact.