speaking of eating mics, if you plan to do any public speaking you should probably learn what placement all the common mics have. it'll help you a lot. Especially with the very common ones with the wire mesh ball that usually need you to be very close to them for it to transmit well over the speakers to a large audience. but some don't want that
megaphones require you to basically kiss them
Vocal microphones are highly directional*, the better to not pick up crowd noise or (in music) other instruments. They are meant to be pointed at their source*, and they will only* pick up what they're pointed at.
The two common mistakes are too much distance (as @NireBryce says, eat the mic) and pointing it straight up/not at your mouth.
Hold it close enough, and high enough, and point it at the back of your throat, and you'll be more audible than 9 out of 10 other speakers.
(Disclaimer: Some events will have a stage manager whose job it is to point stuff like this out. If they contradict me, take their word over mine! Assume they know their equipment, and follow their direction.)
*Vocal microphones typically have a cardioid polar pattern, which means they can still pick up sounds up to 90 degrees off-axis with reduced sensitivity (this is a generalization; individual mics vary). That reduced sensitivity is the kicker, as a speaking setup may pair the microphone with a noise gate to eliminate unwanted background sounds (e.g.: projector/computer fans, movements of other people on stage, mild wind if outside). The microphone alone will pick you up just fine, but at a lower volume that won't meet the threshold of the noise gate between the microphone and the speakers; the noise gate will effectively mute your mic. You don't need to worry about any of this as long as you aim the mic at the back of your throat, because then you'll be on-axis and thus using the mic at its maximum sensitivity.