Body language is key when presenting. You want to seem like you're 'into' the presentation and make it seem like you are passionate about the speech. If you claim you're passionate about your topic, but then have zero facial expressions and aren't using any gestures during the speech, the crowd will most likely lose interest and tune you out. Personally, I love it when speakers use facial expressions and gestures because it draws me in and makes me feel apart of the conversation. If they are passionate, I'm more willing to actually listen because they actually care.
I definitely agree using body language is definitely a good way to show that you really care about something.
I totally agree about having good facial expressions. It definitely keeps people focused on the speaker and what they're talking about.