The Terminator is an 80s classic and considered one of the best action films ever made. For those who have heard of or seen Terminator 2, I have to tell you; Terminator 1 has a very different feel. In T1, the atmosphere is very turbulent. The characters are in constant danger and peril. There is little to no humor. While the film is intense action/violence wise, it is even more so emotionally wise. The prospect of a dark and dreary future where humans must fight machines to survive is unsettling for young children, even older people. The main villain is, well, a cyborg. It is different from most villains because it doesn't feel anything: pain, nor remorse nor pity. Forget Arnie's friendly bodyguard character from T2, this is a ruthless killing machine.
Language isn't as bad as I expected. F-words fly by faster than you can notice them but the profanity isn't excessive and is used smartly.
Sex and nudity wise, there are scenes in this movie. One lasts about six seconds and isn't very explicit. The second one SPOILER ALERT! happens between the two major characters. But as mentioned in other places, it doesn't feel like an R-rated sex scene. It is much more romantic and emotional than sexual. Characters are only shown from the waist up and more is suggested than shown. BTW, the music is amazing and the scene itself is beautiful. Nothing a mature 13+ kid can't handle.