Take a rope and pull it tight. That single physical act, to stretch, is the whole root. Once something is pulled taut it is under strain, and Hebrew lets that strain travel everywhere: a stretched muscle, a wire under voltage, a room full of nervous people, the suspense in a thriller. Even a prank lives here, because to pull a prank on someone is, idiomatically, to "stretch" them. The thread is always the same: a force that pulls and the strain it creates. Pour מ־ת־ח into a verb for the act of stretching; into a noun for the tension that results. Every word here is verified against pealim, niqqud included.
The same root runs through the verb system. Each binyan is a voice: it bends the one idea into active, passive, causative or reciprocal. Tap to hear.
The active pa'al (you stretch the rope) pairs with the reflexive hitpa'el (you stretch yourself, the rope stretches out). That active-and-reflexive pair is exactly what a stretching action needs: someone who pulls, and the thing that gives. The other binyanim are not lexicalized for this root.
Same root letters, different noun moulds (mishkalim). The mould tells you the function: who does it, the act of doing it, or the thing produced.
Strip the prefixes, suffixes and vowels. Three consonants remain, and the meaning lives there.