I was Air Force and do not understand the way the Army names rank. My Son in Law is a Sergeant First Class and just is finishing a second leadership type of course that will qualify him to advance. What will be his rank after promotion? I think he is E-7 now. In the Air Force an E-7 was way up in rank, not quite walking on water, but able to leap large bodies of water. Enlighten me please. He was about to finish his enlistment when 9/11 went down and was stop-lossed and has re-upped since then.

If promoted to E-8, he will be a Master Sergeant or a First Sergeant depending on if he is in leadership. E-7, Sergeant First Class are typically platoon sergeants, but needs of the unit/Army dictate.  Could even be acting First Sergeant at E-7.

First Sergeant is the top enlisted man in a company level unit, normally. Master Sergeant holds an equivalent rank and pay, but he is typically only over seeing a few people. The guy who handled stolen TA-50 replacements at Ft. Stewart when I was there was a Master Sergeant. He worked all by himself. He was a nice guy, and I had to see him a bunch of times for several of my guys.

Enlisted ranks are E1 (Private - recruit) through E9 (Sergeant Major / Command Sergeant Major).

Noncommissioned Officers (NCOs) are your sergeants.

E5 is Sergeant.
E6 is Staff Sergeant.
E7 is Sergeant First Class.  If he is the top NCO in the unit (by duty position) he is typically a Platoon Sergeant.
E8 is Master Sergeant.  If he is the top NCO (by duty position) in a company he is the First Sergeant.
E9 is Sergeant Major.  If he is the top NCO in the unit he is a Command Sergeant Major.

The "Top Three" NCO ranks in the Army are E7-E9.  The difference is especially notable in the Navy.  The Navy's Top Three grades wear (or wore) khaki work uniforms and are "Chiefs" (i.e., Chief Petty Officer, Senior Chief, and Master Chief), while E5s and E6s wear blue sailor working uniforms.

"Khaki Man keeping the Blue Man down."

Thanks for the explanation of the Army way of doing things. Makes it much clearer to me.

Same rank structure as Marine Corps but the acronyms differ and God forbid if you call a Sergeant "Sarge" or Staff or Gunnery Sergeant "Sergeant" too!