The basic types of metric taps explained
Screws, nuts, and bolts are integral parts of any machinery or finished product as well. The industry uses the screws and nuts for fastening purposes. In the past, prior to the Industrial Revolution, the people used wooden nuts and screws. They were huge contraptions, some of them measuring yards in length. It was very difficult to replace them when they wore off. Therefore, there was a need for a new invention. This saw the birth of the metal screws and bolts. These screws and nuts were threaded implements. Hence, you required metric tap and dies to thread them. Except the US and Canada, all countries use metric taps.
You have to do the threading of the screws and the nuts to enable them to bind in a stronger way. The taps and the dies have different duties though the industry uses both of them for forming threads. You make use of the tap to cut or form the threads on the female portion of the tool known in common parlance as the nut. The dies have utility to cut or form the threads on the male portion of the mating pair also known as the screw.
They have other uses as well. You can use these taps and dies for cleaning up the threads. This is the chasing, as you know it in industrial circles. However, you do not use the normal taps and dies for chasing. They could cut through the metal and thereby weaken the threads. Therefore, you make use of special taps and dies known as chasers.  
metric thread taps have great use in every kind of industry. There are many kinds of thread taps. We shall briefly see some of them for the benefit of all. They have a variety of uses in the industry.
Nowadays, you do not see any manual kind of work in the industry. There are machines for every activity. However, the straight flute taps, the simplest ones in the industry, have a manual use. The threads on this tap would be straight. Therefore, you would find the appearance of this thread tap, corrugated.
Not every thread needs to be straight. Circumstances may require an angular thread as well. You can make use of the gun taps to carve out the angular threads. The advantage of the gun tap is that it does a precise job of cutting the thread.
These gun taps have use on the harder metals like iron or brass. In the case of softer ones like aluminum and soft steel, you would require using the spiral flute taps. The advantage of these spiral taps is that they make a deeper and more precise cut.
Some machines or implements would require you to turn the screw anticlockwise to fit tightly. In the normal nut, you would not be able to do it. The reason is that it would be a right-hand nut. You require a left hand tap to carve out the thread in the nut to be able to use the same. The use of the left hand tap is limited. However, you can find left hand taps in the industry.