Need help with loud ticking noise

[bgbchevy]

Just got home from work today, and on the way home i start hearing a real loud tapping noise coming from the engine. I pulled the dipstick and saw that the oil is about a half quart low...I just filled er up today...it usually takes about a month to go through that much. I really havent checked much else because it dark and almost 12:30am....So my question is...What happens whenver you blow a head gasket or burn a valve...what are the "symptoms"

thanks for the help...and I really hope this doesnt turn out to be major