How to compile arm assembly on an m1 macbook

I am completely new to assembly and would like to learn arm assembly (simply because I own an m1 mac). I can't really find many ressources online, that's why I'm here. My code is as follows (file is called first.asm):

global _main
section .text

_main: 
    mov r7, 0x4
    mov r0, 1
    ldr r1, message
    mov r2, 13
    swi 0

.section .data
    message: .ascii "Hello, World\n"

When I use

as first.asm -o hello.o 

I get the following errors:

first.asm:2:1: error: invalid instruction mnemonic 'global'
global _main
^~~~~~
first.asm:3:1: error: invalid instruction mnemonic 'section'
section .text
^~~~~~~
first.asm:6:2: error: unknown use of instruction mnemonic without a size suffix
        mov r7, 0x4
        ^
first.asm:7:2: error: unknown use of instruction mnemonic without a size suffix
        mov r0, 1
        ^
first.asm:8:2: error: invalid instruction mnemonic 'ldr'
        ldr r1, message
        ^~~
first.asm:9:2: error: unknown use of instruction mnemonic without a size suffix
        mov r2, 13
        ^
first.asm:10:2: error: invalid instruction mnemonic 'swi'
        swi 0
        ^~~
first.asm:12:15: error: unexpected token in '.section' directive
.section .data

I have a couple of questions:

1. Is "as" a built-in mac compiler for assembly code?
2. Do I need a different compiler?
3. Does it make sense for me to learn arm assembly since I'm on an m1 mac or could I write x86 assembly without issues?