"Striking while the iron is hot" is an idiom that means taking advantage of an opportunity while it is available. This phrase can be replaced with numerous synonyms that convey the same meaning. One alternative is "seizing the moment," which emphasizes taking action at the right time. Another option is "carpe diem," a Latin phrase that translates to "seize the day." Similarly, "making hay while the sun shines" implies making the most out of a fleeting opportunity. "Taking advantage of a golden opportunity" and "capitalizing on a favorable situation" are also fitting alternatives to this idiom. Regardless of the phrase used, the underlying message is to act quickly and decisively when an opportunity presents itself.