You can define your head and meta properties with the Nuxt Composition API.

You can interact directly with head properties in setup (and within the onGlobalSetup method) by means of the useMeta() helper.

In order to enable useMeta, please make sure you include head: {} within your component definition, and you are using the defineComponent exported from @nuxtjs/composition-api.
import { defineComponent, useMeta, computed, ref } from '@nuxtjs/composition-api'

export default defineComponent({
  // You need to define an empty head to activate this functionality
  head: {},
  setup() {
    // This will allow you to set the title in head - but won't allow you to read its state outside of this component.
    const { title } = useMeta()
    title.value = 'My page'

    // You could also provide an initial value.
    const { title } = useMeta({ title: 'My page' })

    // ... or simply set some meta tags
    useMeta({ title: 'My page', ... })

    // You can even pass a function to achieve a computed meta
    const message = ref('')
    useMeta(() => ({ title: message.value }))