Final answer:
Electric current can easily pass through a metal due to free electrons that move throughout the metal's structure when an electrical field is applied. These conduction electrons enable metals to conduct electricity efficiently.
Step-by-step explanation:
Electric current can pass easily through a metal because negatively charged electrons can move freely within the metal. Metals are known as good conductors because they contain free electrons that are not tightly bound to any particular atom or site, allowing them to move through the metal's structure. When an electrical field is applied to the metal, these free electrons, also known as conduction electrons, wander from atom to atom, contributing to the electrical conductivity of the material.
Within the structure of metals, positively charged metal ions are indeed arranged in a crystalline lattice, but these ions are not free to move. Instead, the sea of free electrons surrounding these ions is what allows for easy current flow. The positive nuclei are tightly packed and contribute to the metal's other properties, such as high melting point and thermal conductivity, but they do not themselves move to carry current.