Eph. 2:1And you hath he quickened, who were dead in trespasses and sins;
2 Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience:
3 Among whom also we all had our conversation in times past in the lusts of our flesh, fulfilling the desires of the flesh and of the mind; and were by nature the children of wrath, even as others.
If "dead" is metaphorical then so must be "quickened" and "saved" (v. 5). Moreover, neither "dead" or "quickened" can refer to physical death or the physical body.
Moreover, this "dead" cannot refer to a non-active entity or cessation of being but is descriptive of a spiritual condition that is manifest in disobedience and rebellion against God (vv.2-3). The cause is internal while the consequences are externally manifested.
Hence, here is a form of death that is due to union with "tresspasses and sins" that is non-material, non-physical but descriptive of the CONDITION of the human spirit that resides within the body that describes all humans who are "without God" and "without hope" (vv.12-13). This is spiritual death that exists as a state/condition of the human spirit FROM BIRTH. Hence, it is not something any post-fallen man EXPERIENCES as a transition from non-spiritual death to spiritual death but a condition of human nature due to the disobedience of one man - Adam "many be dead" which cannot refer to the physical body but to the state/condition of the soul. Hence, only Adam experienced a transition to spiritual death or to a condition of spirit that actively opposed God which transition was manifested by his own act of disobedience. Hence, in Cain and all other posterity that was the condition of the human spirit at conception "already condemned" in a state of unbelief, and tresspasses and sins PRIOR TO committing any conscious personal act of sin.
Hence, the TRANSITION to the spiritual condition of death occurred with Adam manifested by his act of sin whereupon he fell from his moral "upright" condition to a sinful condition of spirit. No such transition occurs in post-fallen mankind such as Cain and Abel as they are "transgressors from the womb." Hence, when Paul says death was "passed" from Adam to all mankind he is referring first and foremost to the immediate state/condition of the spirit of man - spiritual separation/death which eventually ends in this life with physical death and then ultimately the 2nd death.