Not ‘lust’ but this is man’s ‘nature’.

Yes it is like this. Guess what though, women do it too. Its hardwired in their genetics too, the same way. They are looking for the providers and the male that will produce the strongest offspring. First she gazes at the face, since thats an attractor and will help ensure her child will become a good attractor. Second she stares at the main parts of a male body, broad shoulders, chest/torso, pelvic area. Again, this is related to her innate desire to produce a powerful and desirable child. Naturally, since humans aren't just beasts, and they have free will, humans can rise above this and they do. There are still lingering aspects of it in people, it happens. So maybe its called lust to explain a very ancient and innate process.

it is not skin colour or figure which becomes deciding factor for a man when comes to marriage .it is the feminity and vulnerbility which attracts him the most, may be subconsciously as opposite attracts each other .this also satisfy his protecter and provider instinct

Well its very correct coz inspite of our layers of civilization, underneath we are animals and procreation is one of prime aim and duties on this earth. We look at partners and try and measure the capabilities of bearing offspring just as animals test each other. Apart from this, man has of course developed finer instincts which enables him to differentiate between love and lust. That is why the concept of rape is prevalent among humans while the same act is the acceptable norm among animals.