How should a person holding a foreign military rank be addressed?

You would generally put the ranks in English when they are comparable. For example, you would write Colonel Klink rather than Oberst Klink. Using the foreign word is generally the sign of pretentious Sunday-supplement writers trying to sound worldly and “cultured”.

If you are writing a technical assessment or a military history, then you may need to be more precise, like “Grand-Admiral Von somebody (equivalent to a British rear-admiral or a U.S. Navy fleet commander)”.

If there is no comparable rank in English, as with Soviet Commissar or German Führer, then I would use the foreign rank rather than a literal translation.

There are also political considerations to consider, such as how for an Israeli audience, Führer has rather deeper meaning than simply leader.

Your title isn't quite the same as the body of your question: military officers are usually addressed by the simplest form of their rank, such as Colonel for a lieutenant-colonel or General for a major-general; it's a mark of respect, rather than a precise identifier.

If referring to officers in a piece of prose, context is all. A book of Rommel's letters would probably be called The Letters of General Rommel without further specification, since everyone interested knows who is referred to, and understands it covers the period before the subject was promoted to Field Marshal; but the editor might have to specify 'Lieutenant-General Rommel' when explaining why one General was giving orders to another, or even 'Brigadefuhrer Rommel (equivalent to British brigadier or American brigadier-general)' if a point of etiquette came up. Part of this is because many of the Western (not just Latin) languages use similar terms: German, English and French officers can all be generals, but the pronunciation and responsibilities are different. The differences are not, however, important unless the armies are so closely allied that a single chain of command may become necessary, which is why NATO has a set of equivalencies and other countries do not.

In your own case, you need to ask yourself 'Is the distinction between a sergeant and a master sergeant important to this person (or is the distinction in his mind important to me)?' If not (including most civilians), you can simply introduce yourself as 'Sergeant Melamed'. If so, and the person is Israeli, presumably it would be 'Rav Samal Melamed'. Otherwise, the polite way is to use the equivalent in the listener's army, but 'Sergeant First Class' is clear if you don't know how the two compare. 'Master Sergeant' is best avoided professionally (since literal translations can lead to misunderstandings), but it is used in formal contexts; as an example I happen to know, if you were a witness in a British court, the officials (with little or no military knowledge) would be careful not to refer to you merely as Sergeant but the next British rank of Sergeant-Major would be giving you a rank to which you were not entitled, so the precise translation Master Sergeant would be used.