There is a brilliant scene in The Rocketeer where one of the actresses in a theater production is chastised by the director. I couldn't find the scene on YouTube, and my only copy is on VHS, but he tells her something like, "Act, but don't act like you're acting."
And, yes, that is very good advice. There is nothing worse than watching actors do nothing more than read their lines from memory. <shudder> It's horrible.
On the other hand, the truly brilliant actors can act so well that you can tell when they are acting. It's those exceptionally subtle changes they can show in their faces that makes you believe that they are lying to the other characters. Not only do you completely believe that they are the character they are playing, but you know that they are playing a part to mislead someone else.
It's absolutely brilliant.
So, yes, please do more than merely state your lines.
And please don't act like you're acting.
...unless your character is supposed to be acting at that moment in your story.
Your Media Production Mentor