In webhosting, metered and unmetered have different meanings. Meters means that specific amount of bandwidth is allocated to a hosting plan. The bandwidth is measured in terms of GB. Unmetered means that no specific amount of GB bandwidth is allocated, one can use as much disk space as possible.
For a particular hosting plan where unmetered apply, the plan is allocated a specific port size where all the websites in that plan share the resources in that port.
Customers are free to use as much bandwidth as the purchased port can handle. There is no threat of overage costs with an unmetered bandwidth plan because your usage is capped based on the port size you choose. A 100Mbps unmetered port maxed out for an entire month would transmit roughly 33,000GB of bandwidth. A 1Gbps port could transmit 330,000GB (or 330TB) of bandwidth if maxed out for an entire month.
One webhosting company that has unmetered bandwidth is Bluehost.The unmetered bandwidth is specifically on the basic plan that costs $2.65 per month. In that port, there are 50GB storage capacity but the whole plan has unmetered bandwidth. Other plans within shared hosting have unlimited bandwidth, you can check all the plans here
When a site is under unmetered bandwidth, the host will closely monitor how it uses resources and when the limit is exceeded, an email is sent informing the owner to upgrade to a more superior plan.
Check how Bluehost distribute the resources: